在先天性麻痹性斜视中，最常见的麻痹肌是（）

A.下斜肌

B.上直肌

C.上斜肌

D.外直肌

E.下直肌

38.The task is hard, ___, the workers managed to finish it in time.

A．therefore

B．otherwise

C．however

D．yet