第32题: [单项选择]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 参考答案:C 答案解析:[解析] 判断推理题。从文章最后一段最后一句,But the carmakers haven't decided if they will carry it into production becau