--Whose backpack is this?

---It            be Jim’s. Look, his student’s card is in it.

A．must

B．can

C．mustn’t

D．can’t

Duchenne型肌营养不良（）.

A.鸭步

B.跨阈步态

C.剪刀步态

D.醉汉步态

E.慌张步态