You can only be sure of_________ you have at present; you cannot be sure of something _____ you might get in the future.

A．that; what

B．which; that

C．/; that

D．what; /

下列关于肺动脉的叙述，哪一项是错误的

A.3个半月瓣，称为左瓣、右瓣、无冠瓣 

B.肺动脉瓣口位于主动脉口的左前上方 

C.肺动脉瓣各半月瓣游离缘的总部有半月小结 

D.肺动脉口与右室流出道连接 

E.3个半月瓣，称为左瓣、右瓣、前瓣