In the Philippines ， a red tide was first seen in the province of Bataan in 1908. Since then ， red tides have been seen in many other 77 . A Philippines red tide expert told us that “ 78 the fish kills ， the Philippines has documented 1926 cases of dead shellfish poisoning caused by red tides.”
The term “ red tide ” 79 the discoloration of water that sometimes occurs in certain areas of the ocean or sea. Although the color is often red ， it may also be 80 of brown or yellow. The World Book Encyclopedia reports that “ the discolored areas may range from 81 a few square yards to more than 2600 square kilometers.”
What causes such discoloration ？ Red tides are generally caused by several 82 of single-celled organisms. These tiny organisms have hair-like projections which they use to
83 themselves in water. There are about 2000 varieties of these organisms ， 30 of which carry poisonous 84 . These minute organisms usually stay in warm waters with high content of salt.
A red tide occurs when there is a sudden and rapid 85 of these organisms. The concentration of these organisms may 86 to 50000000 per quart of water ！ Although scientists do not fully understand why this happens. It is known that these organisms 87 when certain conditions simultaneously affect the water. These include abnormal weather ， 88 temperatures ， an oversupply of nutrients in the water ， a generous 89 sunlight ， and favorable water currents. When a heavy rainfall occurs ， minerals and other nutrients are sometimes washed 90 the land into coastal waters. These nutrients can contribute to the breeding of the organisms. The result ？ Red tides ！
71. A. As a result B. As it is C. As expected D. As usual
72. A. satisfaction B. disappointment C. astonishment D. regret
73. A. ashore B. aboard C. aside D. across
74. A. question B. crisis C. phenomenon D. situation
75. A. occupied B. occurred C. acquired D. accused
76. A. assured of B. worried about C. concerned about D. aware of
77. A. sandy beaches B. river mouths C. coastal areas D. reef areas
78. A. except B. besides C. despite D. without
79. A. applies to B. sums up C. copes with D. leads to
80. A. shadows B. shades C. shakes D. shapes
81. A. less than B. more than C. as much as D. as little as
82. A. components B. elements C. ingredients D. species
83. A. propel B. probe C. proceed D. prompt
84. A. materials B. substances C. masses D. objects
85. A. bolt B. block C. bloom D. blast
86. A. scale B. plunge C. gauge D. swell
87. A. accelerate B. accommodate C. accumulate D. accompany
88. A. optimum B. minimum C. maximum D. momentum
89. A. means of B. amount of C. way to D. account for
