制作LED灯的发光二极管主要使用的是（　　）

甲、乙两辆汽车沿同一路线赶赴距出发地480千米的目的地，乙车比甲车晚出发2小时（从甲车出发时开始计时）．图中折线$OABC\text{'}$、线段DE分别表示甲、乙两车所行路程y（千米）与时间x（小时）之间的函数关系对应的图象（线段AB表示甲出发不足2小时因故停车检修）．请根据图象所提供的信息，解决如下问题：

（1）求乙车所行路程y与时间x的函数关系式；
（2）求两车在途中第二次相遇时，它们距出发地的路程.

根据短文内容，选择正确答案。

     Dabing and Xiaowei usually go to school by car. They drive past a cinema, a supermarket and a toy shop. The toy shop is next to the supermarket. Yaya and Xiaoli usually go to school by bus. They go past a bank and a post office. The bank is next to the post office. Longlong usually goes to school by bike. He passes by a police station, a library and a swimming pool（游泳池）.