Early and modern theories

Correct answer: D. Because it was considered a remnant signal of the early hot universe

This radiation supports the early hot state of the Big Bang. In exams, treat it as evidence against steady state.

Correct answer: A. Both link the solar system with cloud-like material

Kant's idea was not as complete as the modern model, but the cloud-like source idea is similar. In exams, look at both similarity and limitation.

Correct answer: B. The unclear physical process of stable planets forming from rings

The modern model explains planet formation through stages such as condensation and accretion. In exams, separate the old idea's limitation from the modern process.

Correct answer: C. Small solid bodies joining to form larger bodies

Accumulation of planetesimals matches the basic idea of accretion. In exams, remember the order from smaller to larger bodies.

Correct answer: D. A close passing star is rare and hot ejected solar matter is difficult to form stable planets

The tidal theory is weakened by the rarity of the event and the hot-matter problem. In exams, write both limitations together.

Correct answer: A. Because planets formed in a flat rotating disk

Bodies formed in a flat disk are generally arranged in a similar plane. In exams, connect disk and orbital plane.

Correct answer: B. Ordered similar-direction motion of planets

Bodies formed from one rotating original disk show similar motion. In exams, connect angular momentum with planetary motion.

Correct answer: C. Icy materials and gases could remain there in larger amounts

In the cold outer region, accumulation of ice and gases became possible. In exams, connect the frost line with planetary composition.

Correct answer: D. In the hot region light gases were less and rocky-metallic materials dominated

Near the Sun, heat and solar winds made retention of light gases difficult. In exams, understand inner planets as rocky and dense.

Correct answer: A. Icy cores and greater gas accumulation in colder regions

Low temperature in outer regions allowed gas and ice to remain. In exams, connect outer planets with cold regions and gas accumulation.

Correct answer: B. They helped remove light gases

Solar winds reduced light gases in the inner region. In exams, remember the role of solar winds in the rocky nature of inner planets.

Correct answer: C. Planet formation in protoplanetary disks

Disks around young stars are observational support for the solar nebula model. In exams, connect modern evidence with the model.

Correct answer: D. Leftover early construction material of the solar system

Remnant bodies provide information about early solar-system material. In exams, study them as remnant evidence of planet formation.

Correct answer: A. Conditions formed for early matter and light elements

Expansion and cooling created conditions for early matter formation. In exams, connect cooling with cosmic chemical evolution.

Correct answer: B. They became the broad cosmic basis for later stars and solar nebula material

Light elements were early material of broad cosmic evolution. In exams, place Earth in the wider cosmic sequence.

Correct answer: C. The universe's average density and form remain same

The steady state theory tried to maintain average uniformity despite expansion. In exams, connect continuous creation with average density.

Correct answer: D. The universe had an early hot state and expansion

Background radiation is evidence of an early hot state and red shift is evidence of expansion. In exams, connect both evidences with the Big Bang.

Correct answer: A. First accretion increased mass, then differentiation occurred after heating and melting

Accretion builds the planetary body and differentiation organizes its interior. In exams, do not reverse the sequence.

Correct answer: B. It allowed heavy and light materials to separate according to density

In molten state, materials remained mobile and differentiation became possible. In exams, treat melting as a condition for layer formation.

Correct answer: C. Density-based differentiation

Heavy metallic materials moved toward the center and formed the core. In exams, connect iron, nickel, and core with differentiation.

Correct answer: D. Mantle and upper crustal parts

Lighter materials stayed above and helped form outer solid parts. In exams, connect silicate materials with crust and mantle.

Correct answer: A. Heating, melting, and differentiation

These heat sources kept early Earth hot and dynamic. In exams, connect heat sources with internal structure.

Correct answer: B. It released water vapour and other gases from Earth's interior

Outgassing supplied the gaseous material of the early atmosphere. In exams, write gas release and atmosphere together.

Correct answer: C. Later formation of oxygen-rich atmosphere through biological processes

Free oxygen increased later due to activities of photosynthetic life. In exams, do not treat the early atmosphere as present-like.

Correct answer: A. Cooling condensed water vapour and solid crust provided a base for water retention

Cooling, condensation, and a stable surface were all important for the hydrosphere. In exams, write the stages together.