问题 多项选择题

对部分实施因子试验的理解,下面说法正确的是()

A.混杂现象的出现是完全可以避免的

B.混杂现象的结果是可以选择的

C.任何主效应与二阶交互效应的混杂都必须避免

D.存在某些二阶交互作用的混杂通常是可以允许的

答案

参考答案:B, D

单项选择题 A2型题
阅读理解

阅读理解。

     Africa is home to nearly 700 lakes and rivers. It holds the largest amount of water on earth. Because of

the overuse of the lakes, natural climate changes and other factors (因素), these lakes are disappearing quickly.

     Millions of people in Africa depend on water sources like lakes and rivers for their daily water. In other

words, they cannot live without these lakes and rivers. Recent studies by the United Nations show that this

loss of water supply is putting a great pressure on the African population.

     In the 1960s, Lake Chad was nearly 83,200 square feet large. In about forty years, it has lost 95% of its

size and it has almost completely dried up. At one time, it was one of the largest lakes in the world, and was

around 960,000 square feet around 6,000 years ago.

     The sizes of lakes and rivers and the amount of water have something to do with seasons naturally. But,

pollution and agriculture also play an important part in the loss of water. Many pollutants (污染物) are put into

lakes and rivers so that many lakes and rivers are seriously polluted, and the water may be poisonous (有毒的).

If something isn't done soon about the disappearing lakes and rivers, there will not be enough water for

everyone. Then many people in Africa will face diseases and possible dehydration (脱水).

1. What can we infer from the first paragraph? [ ]

A. There are about 700 lakes and rivers in Africa.

B. Africa is the largest continent on earth.

C. As climate changes, there is less and less water in Africa.

D. Now Africa has less water than before.

2. The figures in the third paragraph show _____. [ ]

A. more and more lakes are drying up

B. Lake Chad was a large lake

C. how quickly water is being lost in Africa

D. Lake Chad is 4,160 square feet now

3. Which of the following is NOT one of the results of the loss of water in Africa? [ ]

A. African people's daily life is affected.

B. Agriculture develops quickly.

C. The number of population in Africa will be smaller.

D. Many people will suffer from diseases.

4. What is the purpose of the passage? [ ]

A. To explain why lakes and rivers are disappearing in Africa.

B. To show people the results of the loss of water in Africa.

C. To call on people to solve the problem of the loss of water in Africa.

D. To tell people how to protect the lakes and rivers in Africa.