Although vehicles are becoming more and more important as the means of transport in modern life, why do they also cause many problems

【参考答案】

Because the number of cars is increasing。 见第一段第二句。题中的前半句题干很明显的是第一段的第一句，所以我们要回答的内容肯定是文中But后的部分。with正好引出了这个原因。