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