he lost one of the books which borrowed from A were B was C

he lost one of the books which borrowed from A were B was C had D have 为什么不能选A?

C是错误的.应该是had been.
He lost one of the books which had been borrowed from thelibrary.
再问： 那用were不行吗？
再答： 用were这里有点不妥，因为被借动作发生在丢失之前。所以要用had been。 补充一点，假如有特定的时间状语如last year，yesterday等，可以用were。 希望对你有所帮助。