plastic theory

例句：

1. 1.The new car has a plastic exterior.
   这辆新车有一个塑料外壳。
2. 2. Plastic bags are often used for shopping.
   塑料袋通常用于购物。
3. 3.The scientist discovered a new type of plastic that is stronger and lighter than traditional ones.
   这位科学家发现了一种新型塑料，比传统塑料更坚固、更轻便。