单项选择题

Questions 17—20 are based on the following text about energy. You now have 20 seconds to read Questions 17—20.
What is the use of greenhouse gases

A．They allow energy from the sun to enter but prevent energy from leaving.
B．They allow energy from the sun to leave but prevent energy from entering.
C．They protect the plants.
D．They protect the earth.

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单项选择题

Which of the following statements is NOT true according to the passage

A．Before 1949, Americans didn’t use any card.
B．There are from 15,000 to 19,000 different cards available in his country.
C．The revolution of credit card that began in 1949 with an embarrassed businessman.
D．The first to turn a profit was Bank of America’s Bank Americard.

单项选择题

Which of the following statements is TRUE, according to the author

A．Everyone has a right to hold his own opinion.
B．Free expression of opinions often leads to confusion.
C．Most people tend to be careless in forming their opinions.
D．Casual use of the word "opinion" often brings about quarrels.

Questions 17—20 are based on the following text about energy. You now have 20 seconds to read Questions 17—20. What is the use of greenhouse gases 您的浏览器不支持 audio 元素。

Questions 17—20 are based on the following text about energy. You now have 20 seconds to read Questions 17—20.
What is the use of greenhouse gases