单项选择题

The most important requirement to have a life-supporting zone in any solar system is that it must have

A．enough water and proper temperature
B．enough oxygen and hydrogen
C．enough air and sunlight
D．enough water in any state
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单项选择题
The goldilocks zone mentioned in the 5th paragraph most probable means ______
A．a certain fixed distance between a planet and sun
B．a range in the universe in which the planets' temperature is suitable for life
C．a range in the universe in which the planets can receive enough sunlight
D．a mathematical model to measure the size of the planetary system
单项选择题
It is suggested in this passage that _____.
A．scientists have found evidence to prove there are many Earth-like planets in our galaxy
B．theoretically there are a great number of Earth-like planets capable of supporting life
C．our Earth is the only planet in our galaxy that can support life
D．with more powerful telescopes, scientists will be able to find more galaxies in the universe
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