Fred liked fish very much, and when he had enough money, he bought some in the market, and took it home. But when his wife saw the fish, she always said to herself,' Good! Now I will invite (邀请) my friends to lunch and we will eat the fish. They like fish very much. 'So when Fred came home in the evening, the fish was never there, and his wife always said, 'Oh, your cat ate it! She is a very bad animal!' And she gave Fred soup(汤) and bread for his dinner. But one evening when this happened, Fred became very angry. He took the eat and his wife to the shop near the house and weighed (秤重) the eat carefully. Then he turned to his wife and said, 'My fish is here, you see, then where is my cat?' Fred always bought fish in the market when ______.