开放性神经管缺陷可导致羊水 （）

A.AFP降低

B.AFP升高

C.肌酐降低

D.肌酐升高

E.黏多糖沉积

----Did you _________ your friend when you were in Beijing?

---No. But I _________ my aunt’s during my stay there.

A．call on; called on

B．call at; called at

C．call on; called at

D．call at; called on