Sources of information

Drilling gives real samples but depth is limited. Exam tip: write both use and limitation of direct sources.

P waves can pass through liquid but S waves cannot. Exam tip: connect this comparison with outer core.

Records from many stations explain wave paths better. Exam tip: treat multi-location data as reliable evidence.

Gravity clue is indirect. Exam tip: use rock sample or combined evidence for chemical composition.

Different sources provide different information about the core. Exam tip: draw conclusions from combined evidence.

Meteorites are useful for comparison but do not come directly from Earth's interior. Exam tip: write them as indirect evidence.

Geothermal gradient shows temperature change and radioactive decay can provide heat. Exam tip: separate observation and cause.

Shadow zone forms due to wave behavior in internal layers. Exam tip: connect it with nature of the core.

At Moho properties change between crust and mantle. Exam tip: remember Moho through wave velocity change.

Gutenberg boundary is considered between mantle and outer core. Exam tip: link it with seismic wave change.

Lehmann boundary is linked with outer and inner core. Exam tip: treat it as an internal core boundary.

Direct answer: A, incorrectly extending the scope of the sample. A mine sample is direct evidence from a limited part of the crust. It can help us learn about that sampled location or similar crustal material, but it cannot by itself prove the composition of the deep core. The reasoning is: source collected in the crust has a limited range; the core is much deeper and has different pressure, temperature and materials; therefore the same sample cannot automatically represent it. Option A is correct because it identifies the limitation and overextension. Option B is about using a seismograph, which is not the error described. Option C refers to confirming a gravity clue, but no such confirmation is given. Option D concerns magnetic study and is also unrelated. Exam cue: never apply evidence beyond the region or object from which it was obtained.

Drilling gives real samples while seismic waves give clues. Exam tip: remember the difference between sample and clue.

Information from a source can usually be applied only within the part of Earth that the source directly represents. Rocks collected from the ocean floor are samples of the oceanic crust. They can provide evidence about the crust’s composition, age and formation, but they do not directly show the conditions or materials of the deep core. The core lies far below the crust and cannot be examined simply by collecting ordinary surface rocks. Scientists therefore use other evidence, such as seismic waves and Earth’s mass, to study deeper layers.

Option A is correct because it properly limits the scope of ocean-floor rock evidence to the oceanic crust, not the core. The rocks are genuine rocks, so B is false. They do not come from the atmosphere, and they are not merely rainfall records. The key reasoning is that evidence must match the layer from which it comes. Applying crustal evidence directly to the core would extend the source beyond what it can reliably demonstrate.

Volcanic material is useful but its origin and limits must be understood. Exam tip: write both usefulness and limitation.

Borehole temperature is useful but does not reach very deep Earth. Exam tip: write limitation of direct thermal data.

S waves do not travel in liquids so absence indicates liquid state. Exam tip: do not link it with emptiness.

Change in P wave path indicates change in medium properties. Exam tip: connect refraction with core boundary.

Higher mean density indicates dense internal materials. Exam tip: connect density argument with the core.

Artificial waves are controlled indirect geophysical method. Exam tip: write clue based methods as indirect.

Arrival time helps infer wave speed and path. Exam tip: understand seismogram as an analytical record.

The direct answer is A: body waves pass through Earth’s interior and are affected by internal materials. P waves and S waves travel through the Earth after an earthquake. Their speed, direction and arrival pattern change when they meet materials of different composition, density or state. Scientists compare recordings from many places and infer boundaries such as the crust, mantle and core. P waves can travel through solids and fluids, whereas S waves do not travel through fluids; this difference gives important evidence about the interior. Option A is correct. B describes surface damage, not their main scientific use. C is false because they are seismic waves, not weather signals. D is unrelated. Memory cue: body waves go through the body of Earth.

Both processes indicate boundary and medium change. Exam tip: remember their difference and use together.

Both clues are indirect and comparison strengthens conclusion. Exam tip: separate possible and definite conclusions.

Mining and drilling have limited reach. Exam tip: write seismic and other indirect sources for deep parts.