I’m sorry,a number of books A.is lost B.is missing C.are missing D.are missed .

I’m sorry,a number of books A.is lost B.is missing C.are missing D.are missed .
I’m sorry,a number of books A.is lost B.is missing C.are missing D.are missed .

I’m sorry,a number of books A.is lost B.is missing C.are missing D.are missed .
选C
a number of只是表示数量的定语,修饰复数主语books,系动词要用复数的are,排除A和B
missing是形容词“失踪的、找不到的”,用作表语；而are missed被动语态,意思是“被错过、被遗漏、未被察觉等”,属于词义错误,故排除D.

选are missing

c

C
a number of作主语时谓语动词要用复数，故排A与B，而 missing 作形容词’丢失的‘，再排除D

C a number of books book可数又用了复数 所以后面是are
意思是 不好意思，很多书丢了