The socks are so ______ that they can't be mended any more.

A．used up

B．worn out

C．tired out

D．broken out

粪便带粘液，并且粘液常在粪便前流出，多见于以下何种疾病：（）

A.直肠息肉

B.肛裂

C.肛瘘

D.内痔

E.肛窦炎