单项选择题

There is supposed to be a safety ______ which makes it impossible for trains to collide.

A．appliance
B．accessory
C．machine
D．mechanism
<上一题 目录 下一题>
热门 试题

单项选择题
Although the colonists ______ to some extent with the native Americans, the Indians' influence on American culture and language was not extensive.
A．migrated
B．matched
C．mingled
D．melted
单项选择题
______ is the center of our planetary system was a difficult concept to grasp in the Middle Ages.
A．It is the sun and not the earth
B．Being the sun and not the earth
C．The sun and not the earth
D．That the sun and not the earth
相关试题