用括号内所给动词的适当形式填空，必要时可加助动词或情态动词。

    Last year my English class was difficult. First of all, it wasn't easy for me 1.______ (understand) the

teacher when she talked. 2.______ (begin)with, she 3.______ (speak) too quickly,and ! didn't understand every word. I was also afraid of 4.______ (speak) in class, because I thought my classmates 5.______ 

(laugh) at me. I 6.______ (make) complete sentences, either. Then I started to watch English-language

TV. It helps me a lot. Now I am enjoying 7.______ (learn) English and got an A this term.

1. _______2. _______3. _______4. _______5. _______ 6. _______7. _______

不锈钢焊件焊接缺陷应采用钻削、铣削、砂轮磨削等机械方法清理缺陷，焊接前应清理焊缝两侧各（）mm范围内的油、水、锈等污物。

A.10

B.15

C.20