液压控制阀根据用途可分为压力控制阀、流量控制阀、（）等。
参考答案：方向控制阀
反意疑问句专练。
1. They are American, _____?
2. There is a clock on the wall, _____?
3. that's not a cat, _____?
4. Jim can't play the violin, _____?
5. Mary makes a lot of friends, _____?
基差交易
