.

--- What do you think our guests ___________ be doing at the moment?

--- They must be enjoying themselves at the party.

A．can

B．must

C．should

D．would

关于反复搏动的表述，不正确的是（）。

A.指激动传导过程中发生回折，使激动起源的心腔再次被除极

B.反复搏动一定有房室交界区的参与

C.属于一种特殊形式的折返

D.仅表现单次折返

E.发生反复搏动最常见的部位是房室交界区