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.

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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

单项选择题

We can infer from the passage ______.

A．an intelligent robot will replace human workers in the future
B．an intelligent robot cannot replace human workers in the future
C．an intelligent robot can do their work good and fast without any mistakes in the future
D．none of them