是什么导致的事故仍然是个谜。( )
A.It is still a mystery what caused the accident. B.It is still a mystery that caused the accident. C.It is still a mystery in which caused the accident.正确答案A
是什么导致的事故仍然是个谜。( )
A.It is still a mystery what caused the accident. B.It is still a mystery that caused the accident. C.It is still a mystery in which caused the accident.正确答案A