问题
选择题
It was not until yesterday _____ I realized how important English was.[ ]
A. when
B. that
C. which
D. what
答案
答案：B
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It was not until yesterday _____ I realized how important English was.[ ]
A. when
B. that
C. which
D. what
答案：B
该光子后被电离，电离后电子的动能为零