Professor Green, known to the world as a scientist, is not only absent-minded but short-sighted as well. His mind is always busy 41 scientific problems and seldom notices what is going on 42 him. One fine day recently, he went 43 a walk in the countryside, but as 44 he has a book in his hand. When he went out , he began to read his book . He hadn’t gone far 45 he run into a big cow and fell down. In the fall, he had lost his glasses, without which he couldn’t see anything. He thought he had hit his head 46 a fat lady. “I’m sorry, Madam.” He said politely 47 searching for his glasses. As soon as he had 48 , he realized his mistake. Soon he was fixing his mind on his book 49 and paid no attention to anything else. He had scarcely been walking for five minutes when he fell over again, _50 both his book and his glasses. This time he got very angry, seizing his umbrella, he gave the “cow” a wild blow. Then, after finding his glasses, he realized with horror that he made a second mistake. A large fat woman was fleeing from him in a horror. 44( )