Shelly had prepared carefully for her biology examination so that she could be sure of

passing it on her first ____. [ ]

A. attraction

B. attempt

C. arrival

D. article

以下哪项是直肠排便功能重要的环节（）

A.直肠下段发生排便反射

B.结肠的蠕动，粪便下行

C.直肠能分泌黏液

D.外括约肌的自主松弛

E.腹压的增加