单项选择题

According to Lemaitre , the separate galaxies formed

A．during a pause in the expansion of the universe.
B．at the time of the primeval explosion.
C．and will continue to form for ever.
D．about 20, 000 million years ago.

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单项选择题

We see distant galaxies as they were long ,long ago because

A．they were closer together then.
B．the universe has always looked as the same.
C．their light takes so long to reach us.
D．they have travelled such a long way.

单项选择题

What is the basic difference between the two classes of theories

A．It concerns the place and time of the formation of matter.
B．It is whether the universe will continue to expand or not.
C．It is the current state of the universe.
D．The variations on evolutionary theories cause the difference