Einstein was born in 1879 in Germany. As a child, he was slow to learn to talk. As a pupil, he was backward. But when he was fourteen years old， he became clever. He taught himself math from textbooks. He studied hard because he wanted to be a physicist.
In 1901，Einstein began teaching. In 1902 he continued his studies at the University of Zurich. Several years later, he formulated (系统地阐述)his famous Theory of Relativity (相对论). To most people the law of relativity is difficult to explain. But once Einstein explained it very well to a group of young students. He said, "When you sit with a good girl for two hours, you think it is only a minute. But when you sit on a hot stove for a minute, you think it's two hours. That is relativity."
After Hitler came into power in Germany, Einstein went to America. In 1940 Einstein became an American citizen. In 1955， Einstein's life ended at the age of seventy-six.
The law of relativity is ______ .

A．very hard for most people to understand

B．too hard for Einstein himself to explain

C．too hard to explain to anybody except Einstein

D．easy to understand only for the young students

When did Einstein become an American citizen?

A．He was an American citizen until 1940.

B．Not until he had reached the age of 61 did he become an American citizen.

C．He did not become an American citizen until 1955.

D．He became an American citizen in the year when Hitler came into power.

Which of the following do you think is true?

A．The Germans owed their scientific progress to Einstein.

B．The Americans owed all their economic development to Einstein.

C．Einstein owed a great deal to the modem world.

D．Einstein made a very great contribution to modem science.

The title for this passage should be "______ ".

A．Theory of Relativity

B．An American Citizen

C．Albert Einstein

D．Einstein's Contribution