单项选择题

The noise-killing system is not yet popular mainly because ______.

A．it is still being tried out
B．drivers still have their doubts
C．it increases the cost of car production
D．carmakers are not sure if it is necessary
<上一题 目录 下一题>
热门 试题

单项选择题
Besides its main use the noise-killing system can ______.
A．make a car lighter
B．make a car quieter
C．reduce the cost of a silencer
D．improve the performance of a silencer
单项选择题
The underlined word they in the last sentence of the first paragraph refers to ______.
A．birds and parasites
B．birds and sheep
C．parasites and sheep
D．sheep, birds and parasites
相关试题