问题 选择题

已知玉米子粒黄色对红色为显性,非甜对甜为显性。纯合的黄色非甜玉米与红色甜玉米杂交得到F1,F1自交或测交,下列预期结果不正确的是 [ ]

A.自交结果中黄色非甜与红色甜比例9:1

B.自交结果中黄色与红色比例3:1,非甜与甜比例3:1

C.测交结果中红色甜:黄色非甜:红色非甜:黄色甜比例9:3:3:1

D.测交结果为红色与黄色比例1:1,甜与非甜比例1:1

答案

答案:C

阅读理解

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.

单项选择题