—What are those?

—______ students' ID cards.[ ]

A. Those are

B. They're.

C. These're

诊断主动脉瓣关闭不全最重要的体征是

A．心界扩大呈靴形

B．主动脉区第二音减弱

C．心前区抬举性搏动

D．周围血管征

E．第二主动脉瓣区闻及舒张期杂音