单项选择题

What does the passage mainly discuss

A．The production of solar light and heat.
B．The physical and chemical nature of life.
C．The conversion of hydrogen to helium.
D．Radiation in the x-ray part of the spectrum.

<上一题目录下一题>

热门试题

单项选择题

It can be inferred from the passage that the Sun's light travels ______.

A．through solid objects in space
B．in many different directions
C．more slowly than scientists previously believed
D．further in summer than in winter

单项选择题

According to the passage, energy is released in the Sun when ______.

A．helium atoms bind with each other
B．gamma radiation escapes from the spectrum
C．radiation is absorbed by helium
D．nuclei of hydrogen atoms collide