Ex4: Choose the letter A, B, C or D to complete the passage below
   A tsunami is a chain of fast moving waves in the ocean caused by powerful earthquakes or volcanic eruptions. Tsunami has a very long wave . It can be hundreds of kilometers  6)......................Usually , tsunami starts suddenly . The waves travel 7).........................a great speed across an ocean with little energy loss . They can remove sand from beaches , destroy trees , toss and drag vehicles , damage houses and even destroy whole towns.
 The water will draw back from the coast half of the wave period prior to the wave getting to the coast . If the slope of the coast is not deep , the water may 8 ).....................for hundreds of meters . People who do not know of the danger will often remain at the shore . 
 Tsuami cannot 9)...............................However , there are ways to help stop people from dying from a tsunami . Some 10) .....................with lots of tsunamis may use warning systems which may warn the population before the big waves reach the land . Because an earthquake that caused the tsunami can be felt before the wave gets to the shore , people can be warned to go somewhere safe . 
  Question 6:               A. deep                    B. long                         C. high                         D. thick 
  Question 7:               A. of                         B. in                            C. on                             D. at 
  Question 8:               A. raising                  B. arise                       C. raise                        D. rise 
  Question 9:              A. to prevent             B. prevent                   C. be prevented            D. preventing 
  Question 10:           A. waves                   B. traps                        C. areas                        D. slopes