______ is often the case with children, Amy was better by the time the doctor arrived.

A．It

B．That

C．What

D．As

一位风心病二尖瓣病患者，因发热一周住院。查体：肺底水泡音，肝大伴腹痛，下肢水肿。心电示心率130次／分，PR间期0．28s。心脏听诊可听到哪种奔马律（）

A.左心室奔马律

B.右心室奔马律

C.重叠奔马律

D.火车头奔马律

E.房性奔马律