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【单选题】In many stories on TV and in science-fiction books, men travel to faraway stars．They have quick, easy journeys．But so far, men have been able to reach only the earth's own moon. Suppose a man wanted t...
A.
Units of light-years sound better.
B.
Using light-years reduced the number of figures used.
C.
We used to measure distance in light-years long ago.
D.
We do not make mistakes when we use light-years.