While ignorance is harmful, half-knowledge is often misunderstood. Someone went to camp in the wild. He knew that camping under a tree was easy to be struck by lightning, so he chose an open place. His tent became an isolated target on the horizon, as dangerous as camping under a tree. The husband knew that he and his wife were both blood type A and would not give birth to children with type O blood, but his child was actually type O blood, which is worth it! After all the trouble, the husband learned from experts that his blood type is AAAO, and there is a possibility of giving birth to a child with O blood type. The ancients suffered because of ignorance, and the modern people caused suffering because of their ignorance.