Có mấy chỉ số quan trọng thể hiện vai trò số lượng của các nhóm loài trong quần xã?

A. 1.

B. 2.

C. 3.

D. 4.

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 46 to 55

Tsunami is a Japanese word which means harbour wave and is used as the scientific term for seismic sea wave generated by an undersea earthquake or possibly an undersea landslide or volcanic eruption. When the ocean floor is tilted or offset during an earthquake, a set of waves is created similar to the concentric waves generated by an object dropped into the water. Most tsunami originate along Ring of Fire, a zone of volcanoes and seismic activities, 32,500 km long that encircles the Pacific Ocean. Since 1819, about 40 tsunamis have struck the Hawaiian Islands.

A tsunami can have wave lengths, or widths, of 100 to 200 km, and may travel hundreds of kilometers across the deep ocean, reaching speech of about 725 to 800 kilometres an hour. Upon entering shallow coastal waters, the wave, which may have been only about half a metre high out at sea, suddenly grow s rapidly. When the wave reaches the shore, it may be 15m high or more. Tsunamis have tremendous energy because of the great volume of wave effected. They are capable of obliterating coastal settlements.

Tsunamis should not be confused with storm surges, which are domes of water that rise underneath hurricanes or cyclone and accompanying storm surge killed an estimated 500,000 people in Bangladesh in 1970. The tsunami which struck south and southeast Asia in late 2004 killed over 200 thousand people.

What will happen when an object is dropped into the water ?

A. volcanic eruption may be a consequence

B. Some concentric waves will be generated

C. there will be seismic activity

D. Earthquake may happen

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