Bill and Fred are students, and the

Bill and Fred are students, and they're good friends. They don't have much money, so when it is time for their holidays, Bill says, "Let's take our holidays in a trailer, Fred. It's cheaper than a hotel. I can borrow my father's trailer." Fred is very happy, and they begin their holidays.
They want to get up early the next morning to go fishing, but they don't have a clock.
"That's all right, Bill." Fred says, "I put these small pieces of bread on the roof(房顶) of the trailer at night and they will wake us up in the morning."
Bill is very surprised, but he doesn't say a word. Fred is right. Early the next morning, some small birds come down on the roof to eat the bread and they make a lot of noise. Bill and Fred get up when they hear the noise.