练习：
　　1. When does the sea look beautiful?
　　A) When it is calm
　　B) When the weather is fine
　　C) When there is a strong wind
　　D) When there is a storm
　　2. How much of the earth's surface does land cover？
　　A） 15%
　　B） 25%
　　C） 30%
　　D） 45%
　　3. Why does the author cite the sea somewhere near Japan?
　　A) To show that the sea in some places is very deep.
　　B) To show that the sea in some places is very shallow
　　C) To show that its depth is 9 kilometers greater than the height of the highest mountain
　　D) To show that its depth is 11 kilometers greater than the height of the highest mountain
　　4. Which of the following statements about the Dead Sea is NOT true?
　　A) There are plenty of fishes in it.
　　B) It is a safe place for swimmers.
　　C) It is extremely salty.
　　D) No fish can be found in it.
　　5. Why can't people go very deep in the sea?
　　A) Because the deepest part of the sea is very cold.
　　B) Because the deepest part of the sea is very rough.
　　C) Because the pressure of the water at great depths is unendurable.
　　D) Because fierce fish usually live there.
　　Key: BBAAC