secondary generation of oil

例句：

1. 1.The second-floor office is located in the back of the building.
   二楼的办公室位于大楼的后面。
2. 2.The secondary school is a good choice for students who want to advance their education.
   这所中学是那些希望继续深造的学生的好选择。
3. 3. The secondary market is where people buy used goods.
   次级市场是人们购买二手商品的地方。