二尖瓣狭窄或（和）关闭不全时，胸片可见到的表现有（）

A.肺内无结节状影

B.肺内含铁血黄素沉着

C.间隔线

D.上肺静脉增粗，下肺静脉变细

E.肺动脉段凹陷

基本语法

1. I was ill ,so I        __(不得不)stay at home today.

2. You____   (不必)return that book to me at once.

3. We        _ (可能去)to visit my father's farm during the summer vacation.

4. You    ___  (可以)call him. He   __   (不可能)do anything else this afternoon.

5. ______(或许)she will invite you to her party ,too.