按照气动控制元件的作用，顺序阀属于（）
A、流量控制阀
B、压力控制阀
C、方向控制阀
参考答案：B
用所给动词的适当形式填空。
1. Boys and girls. please write notes about ______ ( translate)
2. Do you know is the best advice for ______ (learn) vocabulary.
3. Does you friend often ______ (send ) you email messages?
4. What should you do to improve your ______ (read)?
5. Don't forget ______ (lock) the door when you leave the classroom.
乙醇通过其溶脂性能，破坏粘膜屏障
