selling exchange

例句：

1. 1.The company is selling its products at a discount.
   该公司正在以折扣价销售其产品。
2. 2.They traded their old car for a new one.
   他们用他们的旧车换来了一辆新车。
3. 3. He swapped his old watch for a new one.
   他用他的旧表换了一块新的。