完形填空
A poor woodcutter and his wife lived in the forest in a small hut. It was 1small that it was only large enough for him and his wife2 in.3a cold night, somebody knocked at the door.4woodcutter opened the door and wanted to let the stranger in. His wife said, “I'm afraid we don't have that much space.” The man laughed5 said, “Two can sleep well, three can sit.” And then the stranger6 to come in and they all sat telling stories to each other.
Then came7 knock. The woodcutter told the stranger, “Friend, open the door.” And the man said, “But there is no space.” The woodcutter said, “8 three people can sit 9 four people can sit a little10”.
The stranger opened the door, and a man entered. Suddenly, a strange knock11did not seem to be human's was heard! The woodcutter said, “Open the door. I know who12. It is my donkey.” Everyone said, “13is the donkey going to stand?” The man said 14 all stand when the donkey15 in.
的图象如图，其中a、b为常数，则下列结论正确的是 （ ）