C是错误的.应该是had been.
He lost one of the books which had been borrowed from thelibrary.那用were不行吗？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。