下列不能用于系统卸荷的是（）。
A、直动式溢流阀
B、先导式溢流阀
C、先导式减压阀
D、先导式顺序阀
参考答案：C
世界海洋面积占海陆总面积的百分比是多少？
A 29% B 70% C 71% D 90%
—Did you do __________ on vacation?
---Not really. I just stayed at home and helped mom.
A．something special
B．anything special
C．something serious
D．anything serious
