单选题
公共英语二级
2011-08-18
The noise killing system is not yet popular mainly because__________.
参考答案
C
答案解析
推理判断题。从文章最后一段最后一句，But the carmakers haven’t decided if they will carry it into production because it would add several hundred dollars to the cost of their cars可知，因为费用太高，所以还未确定是否投入生产。
