— I wonder if you can go shopping with me together.

— Sorry. I _____ a letter all the morning and haven't finished it yet. [ ]

A. am writing

B. was writing

C. have written

D. have been writing

适合应用硬化注射疗法的是（）

A.内痔

B.外痔

C.肛漏

D.息肉痔

E.锁肛痔