Aborigines' most common tool in Australia is ________ boomerang, which is used to kill ________ animals.

A．the;/

B．/;/

C．the; the

D．/;the

关于胃肠道的黏膜的叙述，哪项不对（）

A.食管部黏膜有2～4条平行的皱襞

B.十二指肠球部有几条纵行黏膜，有的在幽门处并拢

C.空肠密集的环状黏膜形容为羽毛状

D.回肠黏膜有管腔收缩时可看到环状

E.结肠黏膜纵、横、斜三种方向的都存在