There is supposed to be a safety ______ which makes it impossible for trains to collide.A) applianceB) accessory C) machine D) mechanismA和D有什么区别

There is supposed to be a safety ______ which makes it impossible for trains to collide.A) applianceB) accessory C) machine D) mechanismA和D有什么区别
There is supposed to be a safety ______ which makes it impossible for trains to collide.A) appliance
B) accessory
C) machine
D) mechanism
A和D有什么区别

There is supposed to be a safety ______ which makes it impossible for trains to collide.A) applianceB) accessory C) machine D) mechanismA和D有什么区别
应该选D.safety mechanism 安全机制,而appliance是设备的意思,不合句意.

D貌似不可数

A 器具 器械 装置 D 机械 原理 ，个人感觉D答案倾向于 物理上的那种机械...如果认真辨明词义也可以选出来的

B

A是设备、机械的意思，D一般指“机制”，如The market mechanisms （市场机制）。

A偏向与应用，D偏向于机械化