题目内容
________ it carefully can we hope to find a way to solve the challenging problem.
[ ]
A.When we observe
B.When to observe
C.That we should only observe
D.Only by observing
答案:D
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题目内容
________ it carefully can we hope to find a way to solve the challenging problem.
A.When we observe
B.When to observe
C.That we should only observe
D.Only by observing