根据下列句子及所给单词的首字母，写出各单词的完全形式。

1. I'm w______ that I'll fail the exam.

2. Only then will I have a chance to a______ my dream.

3. All the students must c______ their attention on their work.

4. He worked as a v______ during the Olympic Games.

5. Mr Kennard is a teacher of much e______. He has taught in several countries.

6. —What's the result?

    —My mother will make the ______ (决定).

7. If you work hard, you can ______ (通过) the test.

8. Students need ______(严格的) rules.

9. At ______ (目前) they're too short.

10. But they are always talking about what will happen if I don't ______ (成功).

引起下肢静脉曲张的主要原因是

A．深静脉阻塞

B．髂静脉阻塞

C．静脉压升高

D．静脉壁薄弱

E．静脉瓣损伤