Rain forests cover less than six percent of the earth’s area, but they have 100,000 kinds of all the kinds of plants on the earth. Three-fourths of known kinds of plants and animals call the rain forest their home. Twenty percent of our different kinds of medicine comes from rain forests. The glues on an envelope and in shoes come from tropical plants. Rain forests provide materials for hundreds of other products.

Rain forests are also very important to the world’s climate. The Amazon rain forest alone receives about thirty to forty percent of the total rainfall on the earth and products about the same percentage of the world oxygen. Some scientists believe that the decreasing size of rain forests will affect the climate on the earth, making it uncomfortable or even dangerous for life.

Saving rain forests is an international problem. One country, or even a few countries, cannot solve the problem alone. The nations of the world must work together to find a solution before it is too late.

According to some scientists, what will the decreasing size of rain forests affect on the earth?

What does the passage mainly discuss?

What has Dr. Bauer probably researched?

How many different forms of communication are mentioned here?

According to paragraph 2, parents in Mongolia feed their child's lost tooth to a dog because ______.

The passage indicates that Harvard is___________.

All of the following are mentioned in the passage about supercells EXCEPT that they ________.

The expression get out of hand is closest in meaning to .........

What is the purpose of the passage?

The most suitable title for the passage could be ..............

In order to achieve our goals, we should ...............

Algae remnants found in Africa are________.

All the following are mentioned as possible factors in drawing insects to weakened trees EXCEPT .............

Which of the following is NOT true, according to the passage?

What is the main point the writer is trying to make in the last paragraph?

According to the passage, which of the following is NOT true?

According to the passage, an exuberant tone of voice may be an indication of a person’s ____________.

After which year did the town really begin developing?

The phrase "set off" is closest in meaning to______________.

The expression “traditional methods of teaching” is the first sentence refers to ______

Which of the followings is NOT an evidence of monitoring studying?