It is said that the old coins under the earth for about 100years by the time they were discovered.
A. had buried
B. had been buried
C. buried
D. were buried
网友回答
A. had buried
(答案→)B. had been buried
C. buried
D. were buried
解析：考查时态。by the time+过去的时间，主句用过去完成时态，根据by the time they were discovered.，应选B。句意：据说这些古老的硬币被发现的时候，已经被埋在地下100年了。