Câu hỏi:

Read the followingpassage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions.

      Volcanoes have been erupting on the earth for millions of years.More than five hundred of them still erupt today.These are called active volcanoes.Volcanoes are located in belts or chains.They are found where the earth’s crust is weak.The weak spots let the hot rock escape when the volcano erupts.

      Many volcano belts are mountain ranges along the edges of continents.One belt runs along the western coast of South America up through the western part of the United States.Other volcanoes are found in ocean basins.

      About three-fifths of all active volcanoes in the world are in the Pacific Ocean.Many of these volcanoes erupt under the water.The Hawaiian Islands were built by volcanoes that began erupting under water and finally reached the surface of the ocean.

The passage says that about five hundred volcanoes_____.