下列哪项是二尖瓣行闭式扩张的手术指征（）

A.超声心动图检查可疑左心房内血栓

B.合并妊娠5个月

C.1个月前发生脑梗死

D.3周来发热，血培养阳性

E.心脏拍片及超声心动图可疑瓣膜有钙化

—I hear a traffic accident happened yesterday. Was it terrible ?        

—Yes. A car _____ and all the people in it were badly hurt. But luckily, none of them was killed.      [ ]

A. fell over

B. fell behind

C. fell off

D. fell down to