问题
European scientists announced that the speed of light isn’t the speed limit. —Perhaps it is the biggest challenge to Einstein’s Theory of Relativity. No one _____ any crack in histheory for more than a century. [ ]
A: has found
B: found
C: had found
D: would find
B: found
C: had found
D: would find
正确答案是：
同类题型
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