---who______it be that is knocking at the door?

---It_______be Father, but I’m not sure.

A．can, must

B．can, may

C．must, can

D．may, must

高血镁引起的临床表现哪项不正确（）

A.肌力降低

B.反射降低

C.呼吸肌麻痹

D.昏迷

E.心电图QT缩短