Meteors are rocks from outer space. They hold special significance for scientists because

1. they contain radioactive materials.
2. the earth is made of same materials.
3. they give an idea of other planets.
4. they pass through the atmosphere of earth.

The earth is made up of several concentric layers. The correct order of the layers from the centre to the surface is

1. Crust — Mantle — Core
2. Core — Mantle — Crust
3. Mantle — Crust — Core
4. Mantle — Core — Crust.

Study the figure on the right and complete the analogy:
Continents : SIAL :: …………… : SIMA

1. Mountains tops
2. Ocean floor
3. Plains
4. Volcanoes

This is the densest part of the earth believed to be composed of iron and nickel which is responsible for earth's magnetism. Identify it.

1. Mantle
2. Core
3. Crust
4. None of the above