Let's _________ a snowman.[ ]
A. make
B. take
C. cake
答案:A
判断大动脉关系正常的先决条件是
A.肺动脉瓣下圆锥
B.反位型动脉圆锥
C.主动脉瓣下圆锥
D.双侧圆锥
E.圆锥缺如