阅读下列短文，从短文后各题所给的四个选项(A、B、C和D)中，选出可以填入空白处的最佳选项。
A man who loved to hunt bought two fine setters(特猎犬)that he later trained to be fine bird dogs．He kept them in a large, fenced pen(围栏)in his backyard．
One morning he 41 a little bulldog(牛头犬)corning down the path behind his home. It saw the two dogs and squeezed under the 42 . The man thought he should perhaps lock up the setters so they wouldn't 43． the 1ittle lovely dog. But then he changed his mind .Maybe they would teach that bulldog a1esson, he said to himself
As he predicted，44 began to fly，and all of it was the bulldog’s fur. The intruder(入侵者)soon had 45 and squeezed back under the fence to get away．
