when and why he came here _____ yet.A.is not knownB.are not known_英语解答

when and why he came here _____ yet.
A.is not known
B.are not known
C.has not known

人气：348 ℃　时间：2019-12-24 12:22:24

解答

When and why he came here 作为一个整体,
谓语动词用单数形式..
句意:他何时和为何来这的原因还未知.!'
选AAAAAAAA.