who is singsing in the next room It ( ) my sister.She is going to sing at the party this Sunday.A.can't beB.must isC.must beD.was谢啦、、

问题描述:

who is singsing in the next room It ( ) my sister.She is going to sing at the party this Sunday.
A.can't be
B.must is
C.must be
D.was
谢啦、、

C
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