长行程低速柴油机的阀面与座面配合方式，多采用（）。
A．全接触式
B．外接触式
C．内接触式
D．三种方式均用
参考答案：C
用所给动词的适当形式填空。
1. David often ___________ (help) me with my English.
2. Can you ___________ (put) an egg on your head?
3. Look, the farmers ___________ (pick) apples on the trees.
4. Nancy ___________ (play) the piano at the concert tomorrow.
5. The children went to the farm yesterday. They ___________ (have) fun there.
什么叫三用阀？它是由哪些阀件组成的？
