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?

Which of the following statement is TRUE about the passage?

The expression “readministration” in this passage refers to ................

What is the zone of volcanoes and seismic activity in the world called?

The word "These" in paragraph 3 refers to ..........

According to the passage, when did "the Lord of the Rings" trilogy become popular with young people?

The expression “is based on” in the first paragraph could be best replaced by ..............

Which of the following helps to create the Earth’s magnetic fields?

The passage supports which of the following conclusions?

It can be inferred from the passage that the Puritans who traveled to the Massachusetts colony were __________.

The word “it” in paragraph 3 refers to ........

The word “sensational” is closest in meaning to .............

The word “it” in paragraph 2 refers to ................

According to the passage, what must the nations of the world do to find a solution?

Why does the author mention "artistic, political, or pedagogic communication" in line 14-15?

The underlined pronoun “they”refers to ...............

When Business Week published “ The Portable Executive “, it implied that___________.

From what we read we know that now Cambridge is _______.

Which of the following would most likely NOT be reflected in a person's costume, as it is defined in the passage?

The word “emaciated” in the passage mostly means .......

In order to show that learning to write requires effort, the author gives the example of ................