化合物的系统命名是()。
参考答案:2-甲基-5-硝基吡咯
If you had got up early,you here on time.
A.would reach
B.would have reached
C.have reached
D.had reached
为使电液换向阀工作平稳,常在控制油路中设置()。
A.单向阀
B.单向节流阀
C.节流阀
D.溢流阀