Sam and Joe were astronauts(宇航员). There was once a very dangerous trip and the more experienced astronauts knew there was only a small chance of coming back alive. Sam and Joe, however, thought it would be exciting though a little dangerous. We're the best men for the job, they said to the boss. There may be problems, but we can find the answers. They're the last people I'd trust, thought the boss. But all the other astronauts have refused to go. Once they were in space, Joe had to go outside to make some repairs. When the repairs were done, he tried to get back inside the spaceship. But the door was locked. He knocked but there was no answer. He knocked again, louder this time, and again no answer came. Then he hit the door as hard as he could and finally a voice said, 'Who's there?' 'It's me! Who else could it be?' shouted Joe. Sam let him in all right but you can imagine that Joe never asked to go on a trip with Sam again! Most of the astronauts were unwilling to go on the trip because