A. mice eating more sugar will live longer
B. the study on mice lasted less than a year
C. the study showed the bad effects of more sugar on mice D. mice eating more sugar will bee fatter and fatter 30. Why did the scientists choose mice to do the study?
A. Because a substance may have the same effects on mice and humans. B. Because mice have a longer lifespan (寿命) than other animals. C. Because mice take in the harmful substances easily and quickly. D. Because mice are sensitive to the sweet taste. 31. Which would be the best title for the passage?
A. Living a sweet life
B. Kids eat much more sugar
C. Genetic structure of humans D. Danger of too much sugar
D
Almost everybody in America will spend a part of his or her life behind a shopping cart. They will, in a lifetime, push the chrome-plated contraptions many miles. But few will know—or even think to ask—who it was that invented them. Sylvan N. Goldman invented the shopping cart in 1937. At that time he was in the supermarket business. Every day he would see shoppers lugging groceries around in baskets they had to carry.
One day Goldman suddenly had the idea of putting baskets on wheels. The wheeled baskets would make shopping much easier for his customers, and would help to attract more business.
On June 4, 1937, Goldman’s first carts were ready for use in his market. He was terribly excited on the morning of that day as customers began arriving. He couldn’t wait to see them using his invention.
But Goldman was disappointed. Most shoppers gave the carts a long look, but hardly anybody would give them a try.
After a while, Goldman decided to ask customers why they weren’t using his carts. “Don’t yo