By 2011 the library_____.A.would been built B.had been built C.has been built D.have been built

问题描述:

By 2011 the library_____.A.would been built B.had been built C.has been built D.have been built

B 因为A是将来时,B是过去式,C是现在完成时表示已做,(单数)D是现在完成时(复数)