The reason ______ he was late was unknown.A why B.for which C .that VD.which 多项选择

The reason ______ he was late was unknown.A why B.for which C .that VD.which 多项选择
The reason ______ he was late was unknown.
A why
B.for which
C .that V
D.which
多项选择

The reason ______ he was late was unknown.A why B.for which C .that VD.which 多项选择
A和B都对
Why=for which