单项选择题

The second paragraph is mainly concerned with ____________.

A．how the sun evolved
B．the structure of the sun
C．why scientists study the sun
D．the distance of the sun from the planets
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单项选择题
It can be inferred from the passage that a clear view of the sun's outer layer is usually vented by_______.
A．the sun's rays
B．an eclipse
C．lack of light
D．the great distance
单项选择题
The purpose of the special instruments mentioned in the third paragraph_________.
A．magnify the image of the sun
B．block out the sun's intense light
C．measure the amount of energy emitted by the sun
D．photograph the sun
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