—How about singing songs with me?

—I'm sorry I can't. I ______ help my father with his work. [ ]

A. have to

B. can

C. may

关节被动活动正常，但主动活动受限最可能为（）。

A.神经麻痹

B.关节内粘连

C.皮肤瘢痕挛缩

D.关节强直

E.肌肉痉挛