using Valve.VR;//有关HTC VIVE VR脚本，一定要有这个命名空间

HTC VR C#开发中，（）命名空间是必须的 A: using System.Collections; B: using System.Collections.Generic; C: using Valve.VR; D: using UnityEngine.UI;

A throttle valve is a simple flow control valve, a throttle valve is virtually equal to( ).

The word "valvulotome" means _______________. A: incision of a valve B: an opening of the valve C: an instrument for cutting a valve D: surgical repair of a valve

The commonly used pressure control valve in hydraulic transmission system is ( ) A: directional valve B: relief valve C: hydraulic control check valve

Which of the following hydraulic control valves belongs to pressure control valve （ ）. A: Unloading valve B: overflow throttle valve C: Hydraulic control check valve D: Low pressure selector valve

In order to ensure that the pressure difference between the front and rear of the throttle valve remains unchanged when the load changes, the flow through the throttle valve is basically unchanged. The throttle valve is often connected with ( ) to form a speed control valve, or the throttle valve and ( ) are connected in parallel to form a bypass speed control valve. A: Pressure reducing valve B: constant pressure reducing valve C: overflow valve D: differential pressure relief valve

Valve guide supports the valve stem and guides its movement so that the valve face remains perfectly concentric with the valve seat and fits it without any skewing.

Direct acting relief valve is often used as the pilot valve of safety valve or other pilot relief valve. ( )

Camshaft_____ Valve clearance_____ valve spring______ DOHC_____ timing chain______ valve overlap_______ lifter______ exhaust/intake valve_______