题目内容
Newton was sitting under an apple tree ______ an apple fell onto his head.
| A.when | B.while | C.after | D.before |
A
解析
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Great as Newton was, many of his ideas _______ today and are being modified by the work of scientists of our time.
|
A.are to challenge |
B.may be challenged |
|
C.have been challenged |
D.are challenging |