1. What is the author’s main point?
= Scientists have proposed a radical new model for the make-up of the Earth's core.
2. The main thought of this passage is
= It suggests that differences between the east and west hemispheres of the core are explained by the way iron atoms pack together.
3. The main theme of the passage is
= Seismic data indicate that the western and eastern hemispheres of Earth's inner core differ, and this has led some to suggest that the core was once subjected to an impulse - presumably from the collision of a space rock or planetoid which shook the whole Earth.
4. The best statement of this passage’s main thought is that
= The inner core started to solidify more than a billion years ago. It has a radius of about 1,220km, but is growing by about 0.5mm each year.
5. What is the main idea of the passage?
= Clues come from the speeds that seismic waves generated by earthquakes pass through the core.These tell us its density and elasticity, but the precise arrangement of iron atoms forming the crystalline core controls these numbers.
6. The passage is primarily concerned with
= With all these seismic complexities, the link between the crystal structure and the geophysical observations has yet to be resolved.
7. Which of the following statement express the main idea?
= Dr. Arwen Deuss, a seismologist from the University of Cambridge, commented: "This is a step in the right direction, directly comparing seismology with mineral physical properties." She added that it should eventually provide a better understanding of the birth and evolution of our planet.