在流体系统中，用来控制流体流动方向的阀门是（）。
A、分配阀
B、溢流阀
C、安全阀
D、截止阀
参考答案：A
Anyone can give examples of dreadful damages done by this industry, which is apparently develop with the expense of the environment.
A．which apparently developing at the expense of
B．which apparently develop in the expense of
C．which is apparently developing at the expense of
D．which is apparently developing in the expense of
运动中，因参赛者的水平不一，采用的技能有所不同，但均表现出两项基本技能，这两项基本技能为（）
①随时标定地图
②明确站立点在地图上的位置
③保持连续行进
④路段记忆
A.①②
B.①③
C.②③
D.②④
