阅读理解。
Americans can travel almost anywhere they choose. But to protect its people, the government lists a few
dangerous places where Americans cannot go. These places are unfriendly countries or countries at war.
There, the traveler might not be safe. These countries are listed in a small book called a passport.
This passport is a government request for the safety of its travelling people. It is also a government's
pledge (保证) that the people will obey the rules of the host country.
To receive a passport from the government, a traveler must prove that he is an American citizen (公民).
An American cannot go abroad without a passport. Only certain close countries such as Canada and Mexico
do not ask for passports.
Stuck (贴) inside the passport is the traveler's picture. Children travelling with their parents are included in
one parent's book.
Thousands of people from the United States visit other countries every year. An American traveler might
carry plane tickets, money, clothing and many other things. But the most important thing that he carries in
another country is his passport.
1. A passport is not needed when an American goes to _____.[ ]
A. European countries
B. dangerous areas
C. Canada or Mexico
D. Russia and China
2. It can be inferred from the text that _____. [ ]
A. Americans abroad need nothing except a passport
B. children can't travel to foreign countries
C. a traveler is not safe in most countries
D. Americans travel abroad a lot
3. Which statement does the text lead you to believe? [ ]
A. Some countries don't ask for foreign visitors for passports.
B. People should take good care of their passports.
C. Money is more important than a passport.
D. Children are never included in a passport.
4. Which is best supported by the text? [ ]
A. A passport is needed whenever an American travelling.
B. Everyone in America can get a passport from the American government.
C. The American travelers abroad must obey the rules of foreign countries.
D. The Americans government allows its people to work in dangerous countries.
得到
知轨道半径将加倍，B对；由
知周期将加倍，C对；由
知做圆周运动的角速度将减小为原来的一半，D错。