题目内容
(请给出正确答案)
[单选题]
Not until the end of the 19th century ______ people ______ that the atom was not the smallest particle.
A.do … find
B.did … find
C.were … found
D.have … found
答案
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A.do … find
B.did … find
C.were … found
D.have … found