单项选择题

Why does the photosphere shine so brightly and send out x-rays and ultra-violet light

A．Because atoms are being broken down and built up in the central parts of the sun.
B．Because the photosphere send out light.
C．Because dark spots are much darker than the photosphere.
D．None of the above.
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单项选择题
Why should we care about the extinction of wildlife
A．We need more predators.
B．We are required to by the government.
C．Natural imbalance will threaten human"s life.
D．None of the above.
单项选择题
What is the photosphere
A．Area in the sun where atoms break down and build up.
B．Area of the sun which sends out radio waves.
C．Part of the sun we usually see.
D．Layer of gas which forms the corona.
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