Sources of information

Correct answer: A. Analysis of seismic waves

Crust sample is limited and seismic clues are needed for deep parts. Exam tip: identify the scope of a source.

Correct answer: D. They should be treated as comparative indirect evidence

Meteorites do not come directly from Earth's interior. Exam tip: connect them with comparison of early materials.

Correct answer: A. When it gives a clue of internal material but is not a core sample

Volcanic material comes from inside but does not represent every deep layer. Exam tip: write both use and limitation.

Correct answer: A. They will compare with other evidence and interpret cautiously

Both are indirect clues so verification is needed. Exam tip: write combined evidence for conflicting clues.

Correct answer: C. The first is a possible heat source and the second is limited direct observation

Radioactive decay can produce heat and mine temperature gives a limited clue. Exam tip: separate cause and observation.

Correct answer: D. Combining both according to their scope

Local sample is limited and global seismic data gives depth clues. Exam tip: understand source scope.

Correct answer: A. When it only indicates mass and density

The direct answer is A, when the anomaly only indicates mass and density. A gravity anomaly is an indirect geophysical clue. Gravity depends mainly on how mass is distributed, and density is an important part of that distribution. Different rocks or underground structures can produce similar gravity effects, so the observation alone does not identify a definite chemical composition. The reasoning is: measure a difference in gravitational attraction; infer a difference in underground mass or density; do not directly name the minerals or chemical elements; use samples or laboratory tests for stronger chemical evidence. Option A is correct because it states the limitation of the observation. Option B, laboratory testing of a rock, gives direct evidence from the material itself, so it is not the problematic situation. Option C, an available mineral sample, can be chemically examined and is more direct. Option D, a drilling core, physically brings underground material for analysis and is also more direct. The exam cue is: geophysical anomalies suggest structure or density; laboratory samples reveal composition more directly.

Correct answer: D. Rain gauge and state of outer core

Different sources reveal different parts of the Earth's interior. Seafloor rocks provide evidence about oceanic crust and the materials found near the surface. Seismic waves travel through the Earth and their speed, direction, reflection, refraction, and shadow zones help scientists infer the nature and boundaries of deep layers. Mining samples are obtained directly, but they usually represent only a limited part of the shallow crust because mines cannot reach the deepest regions.

Option D is the incorrect match. A rain gauge measures rainfall, which is a surface weather observation; it does not directly reveal the state or physical condition of the outer core. The other matches are reasonable: ocean-floor rocks relate to oceanic crust, seismic waves provide clues about deep layers, and mining samples offer limited crustal evidence. The question tests whether the source is actually capable of supplying information about the stated part of Earth.

Correct answer: A. Lava is a direct sample of the whole core

The direct answer is A: lava is not a direct sample of the whole core. Lava is molten rock that reaches the surface during a volcanic eruption. It comes mainly from magma generated in particular parts of the crust or upper mantle, so it can provide clues about some interior materials, but it cannot represent every layer of Earth or the entire core. Therefore, the safe reasoning is: lava is volcanic material; volcanic material may reflect some underground composition; the core is much deeper and has different conditions; so claiming that lava is a sample of the whole core is an overextended conclusion. Option A is wrong because it makes a claim far beyond the evidence. Option B is correct as a description because lava is surface material produced by volcanic activity. Option C is also scientifically reasonable because lava can give information about some internal rocks and processes. Option D is important because every source of information has limits, and those limits must be recognised. Memory cue: useful evidence is not the same as complete evidence.

Correct answer: B. Mineral and elemental composition is to be tested

Rock analysis tells composition of real material. Exam tip: choose sample analysis in chemical questions.

Correct answer: A. When temperature and pressure are different at depth

The direct answer is A: it is wrong to decide the state of deep material from a surface sample when temperature and pressure are different at depth. A surface rock can show its mineral composition, but it does not automatically show the physical condition of material far below Earth’s surface. The reasoning is: depth causes pressure to rise and temperature generally to rise; these conditions can change melting, density and the state of rocks; therefore a surface sample alone may mislead us about deep material. Option A correctly identifies this limitation. Option B is not wrong because a local surface rock can be identified by examination. Option C is not wrong because mineral testing is a suitable use of a sample. Option D is not wrong because surface samples and other evidence can help study crustal composition, although they may not reveal the whole interior. Memory cue: a surface sample tells us about the surface, not automatically about deep temperature-pressure conditions.

Correct answer: C. Linking direct samples to their scope and indirect clues to deep structure

Direct and indirect sources give information at different levels. Exam tip: write comparative and balanced answer.

Correct answer: A. When indirect clues still need verification

Indirect clues are verified by comparison with other evidence. Exam tip: use cautious language.

Correct answer: A. Gravity anomaly

Gravity anomaly relates to difference in mass and density. Exam tip: do not treat it as chemical sample.

Correct answer: A. Direct but depth limited evidence

Drilling gives real sample and temperature data but depth is limited. Exam tip: write use and limitation together.

Correct answer: A. When velocity travel time and path data from many stations match

Matching clues from many stations increase reliability. Exam tip: write multi-station evidence.

Correct answer: A. Earth's magnetic field

Magnetic field gives indirect clue of possible metallic materials. Exam tip: do not write it as direct sample.

Correct answer: A. When sample is local and from shallow depth

The direct answer is A, when the sample is local and from shallow depth. A direct sample gives real information about the place and depth from which it was collected, but it cannot automatically represent the entire Earth. Step by step: identify the sample’s source; note that it comes from a limited and shallow area; compare that limited evidence with the much deeper and wider interior; use it carefully alongside seismic waves, gravity, magnetic evidence and other observations. Option A is correct because a local shallow sample has a narrow scope, so its conclusion must be cautiously applied to a whole-Earth model. Option B is not a realistic ordinary direct sample: no routine sample comes from the whole core, and even such a claim would need evidence. Option C, weather, is not a direct rock sample of Earth’s interior. Option D, population, is a human statistic and cannot reveal interior composition. The key lesson is representative evidence: a small observation may be useful, but its conclusion must not be enlarged beyond its limits. Memory cue: local sample, limited conclusion.

Correct answer: A. Volcanic material is Earth derived clue and meteorite is comparative external material

Volcanic material and meteorite are both useful but different in nature. Exam tip: identify source origin.

Correct answer: A. It is very useful but does not give direct sample

Seismic waves give clues and help in deep information. Exam tip: write both use and limitation.

Correct answer: A. Identify source state evidence nature write limitation and give combined conclusion

Expert answer includes role and limitation of source. Exam tip: keep conclusion evidence based.

Correct answer: A. When combined explanation of deep core density and metallicity is needed

Seismic waves show state and boundary while gravity and magnetism give supporting clues. Exam tip: use multi-source analysis.

Correct answer: A. Direct access is difficult due to depth heat pressure so indirect sources are necessary

Deep parts are hard to reach so seismic and other indirect sources are important. Exam tip: write problem and solution together.

Correct answer: A. Direct sources give limited samples and indirect sources give clues of deep structure

Balanced study is based on combined analysis of many sources. Exam tip: write roles of both direct and indirect sources.

Correct answer: C. Multi-station seismic clues will be more useful for the deep boundary

Drill core is direct but local while multi-station wave data indicates deep boundary. Exam tip: draw conclusion according to source scope.