My name is Zhang Peng. I have a friend. His name is John. He has a grandpa and a grandma. They are seventy years old. They are at home. John's father works in a school. His mother is a doctor. John is a good student. They are very busy. They all get up early in the morning. John often helps his grandparents cook breakfast. There is a big garden and many young trees in front of his house. We can play games there. It's great.

边际产量递减规律，指在短期生产过程中，在其他条件（如技术水平）不变的前提下，增加某种生产要素的投入，当该生产要素投入数量增加到一定程度后，再增加该要素所带来的边际量是递减的（如图）。假设可变要素投入量为Q，从图中可以推论出 （   ）

①Q>B时，边际产量为负值，应增加可变要素投入量

②A<Q<B时，由于可变要素投入量过大，导致总产量减少

③Q=B时，边际产量为0，应优化要素配置、提高效益

④Q<A时，由于可变要素投入量不足，导致边际产量没有实现最大化