Early and modern theories

The modern model matches normal physical processes and observations better. In exams, write the difference between a rare event and an evidence-based model.

Kant's idea came before modern evidence but started a natural explanation. In exams, remember both contribution and limitation.

Laplace discussed rings, but the modern model explains processes more clearly. In exams, identify the difference between old idea and modern sequence.

Growth of small building bodies is important in both. In exams, also remember the difference in source material.

The tidal theory cannot satisfactorily explain ordered planetary motion. In exams, treat orbital order as a major limitation.

Bodies formed from one rotating disk can be arranged in similar direction and plane. In exams, write angular momentum and disk together.

Beyond the frost line, icy materials could remain and outer planets grew larger. In exams, connect temperature, distance, and material.

Near the Sun, light gases were reduced and rocky material dominated. In exams, explain inner planets through temperature and material availability.

In the cold outer region, both icy solids and gases were more available. In exams, connect gas giants with cold region and greater mass.

Red shift is a sign of motion in space. In exams, write it as observational evidence of expansion.

Background radiation indicates an early hot state and red shift indicates expansion. In exams, link both evidences with the Big Bang.

The steady state theory imagined creation of new matter during expansion. In exams, remember average density and continuous creation together.

This radiation was considered a remnant of the early hot universe. In exams, remember it as support for the Big Bang and a challenge to steady state.

First the universe and matter formed, then large structures, and later the solar system formed. In exams, remember the large-to-small sequence.

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

Accretion builds the planetary body and differentiation forms its internal structure. In exams, write these processes with order and function.

Heavy materials such as iron and nickel moved to the center and helped form the core. In exams, connect metal, density, and core.

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

Both heat sources played a role in Earth's internal development. In exams, connect heat sources with differentiation.

Gas release produced water vapour and other gases. In exams, connect the early atmosphere with internal gases.

Free oxygen increased through later biological development. In exams, do not treat the early atmosphere as the same as the present atmosphere.

The hydrosphere includes all water on Earth, such as oceans, rivers, lakes, groundwater and water vapour. In the early history of Earth, the planet was extremely hot. As its surface and atmosphere cooled, water vapour could change into liquid water through condensation. The condensed water fell as rain, and over long periods it collected in low areas to form oceans and other water bodies. Therefore, the order must begin with cooling, followed by condensation, rainfall and collection.

Option C gives the correct sequence: Earth cooled, water vapour condensed, rain fell, and water bodies formed. Option A reverses the basic order because stable surface water could not form before the necessary cooling. Option B is incorrect because red shift is an observation related to motion and distance in astronomy, not the process that directly formed Earth’s water. Option D does not describe the accepted sequence. The answer follows a clear cause-and-effect chain.

The solid crust provided a base for hydrosphere and later surface development. In exams, connect crust with Earth's outer development.

The giant impact idea links Moon origin with the active state of early Earth. In exams, treat it as a modern explanation.

The rate of radioactive decay provides a basis for age estimation. In exams, connect Earth's age with scientific evidence.