No matter how long is your life, you will, at best, be able to read only a few books of all that have been written, and _____ few you do read should include _____ best.

A．a; the

B．the; the

C．the; a

D．/; the

对肛管内结构的描述，错误的是

A．肛管上段内面的纵行粘膜皱襞称肛柱

B．相邻两肛柱下端有半月形的粘膜皱襞，称肛瓣

C．肛瓣的边缘与肛柱的下端共同围成齿状线

D．齿状线是肛门内、外括约肌的分界线

E．齿状线下方有宽约1cm的环形区，称肛梳或痔环