A、It was getting dark. B、He was afraid of being blamed by his friend. C、The birds might have flown away. D、His friend would arri

My friend Vernon Davies kept birds. One day he phoned and told me he was going away for a week. He asked me to feed the birds for him and said that he would leave the key to his front door in my mailbox. Unfortunately, I forgot all about the birds until the night before Vernon was going to return. What was worse, it was already dark when I arrived at his house. [20]I soon found that the key Vernon gave me could not unlock either the front door or the back door. I was getting desperate. [21]I kept thinking of what Vernon would say when he came back. I was just going to give up when I noticed that one bedroom window was slightly open. I found a barrel and pushed it under the window. As the barrel was very heavy, I made a lot of noise. But in the end, I managed to climb up and open the window. [22]I actually had one leg inside the bedroom when I suddenly realized that someone was shining a torch up at me. I looked down and saw a policeman and an old lady, one of Vernon’s neighbors.
    "What are you doing up there?" said the policeman.
    Feeling like a complete fool, I replied, "I was just going to feed Mr. Davies’ birds."
20. Why couldn’t the man open the door?
21. Why did the man feel desperate?
22. Why did the man feel like a fool?