Today I’d like to begin a discussion on the problem of the heating up the earth. First, we’ll touch on the relationship between fluorocarbons and the ozone layer. You probably remember that the ozone layer is the protective shield around the earth. It is important to all life, because it filters out harmful ultraviolet light from the sun. Ozone itself, a form of oxygen, is regularly made by the action of the sun in the upper atmosphere. It is also regularly destroyed by natural chemical processes.

The problem now is that too much of the ozone layer is being destroyed. Scientists suspect that certain chemicals, such as fluorocarbons, are contributing to the depletion of the ozone layer. And how do we use fluorocarbons? The most common uses are in spray cans and cooling systems. The chemical pollution from these fluorocarbons can account for some of the ozone losses that have been reported. There are, however, new studies linking the sun itself to the depletion of the ozone layer. We’ll go into that new study more next time.

What is the most important purpose of the ozone layer?

Câu hỏi liên quan

• Which of the following is NOT true?

• The word “classic” in paragraph 3 is closest in meaning to ............

• What does this paragraph mainly discuss?

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• Why is “plankton” mentioned in the second paragraph?

• The expression get out of hand is closest in meaning to_________.

• The word “bodies” in paragraph 3 refers to ...........

• Which of the following is closest in meaning to the word “tuck” in line 11?

• The word "their" in line 12 refers to ......

• The passage would be most interest to...

• How was the public motivated to help the health workers?

• People nod their head to say no in ...............

• All of the following statements are mentioned EXCEPT ______.

• The word “doubtless” in the passage mostly means ...............

• According to the passage, what does a constricted and harsh voice indicate?

• How did John feel about his fears in the end?

• Which of the following pairs is INCORRECT?

• In what year did Melville’s book about his experiences as a cabin boy appear?

• The word “multitudes” is closest in meaning to _________ .

• Algae remnants found in Africa are ..............

• According to the text, the most important quality of a teacher is _______.