问题描述：
one English grammer question
Within the last year,astronomers have come closer than ever___.
A.to deciding which of the questions is right
B.to decide which of the question is right
C.deciding whether the question is right or not
D.and decided which of the questions is right
Within the last year,astronomers have come closer than ever___.
A.to deciding which of the questions is right
B.to decide which of the question is right
C.deciding whether the question is right or not
D.and decided which of the questions is right
问题解答：
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