心肌的异长调节是改变何种因素来调节心脏泵血功能的（）

A.肌浆游离Ca2+浓度

B.肌小节的初长度

C.心肌收缩能力

D.横桥连结数目

E.横桥ATP酶活性

It is said that there are plenty of hotels in that town. There _____ be any difficulty for you to find somewhere to stay.

A．wouldn’t

B．mustn’t

C．shouldn’t

D．needn’t