Imagine fishermen walking down to the seas

题目：

Imagine fishermen walking down to the seashore, ready to carry out their early morning routine of preparing their boats and net. (51) they hope for a good catch of fish. But to their (52) , a horrible sight meets their still sleepy eyes. Thousands of fish have been washed ashore dead. The cause of this mass destruction—A red tide!

Red tides are a global (53) . They have been observed on both the Atlantic and the Pacific coasts of the United States and Canada. They have also occurred in many other places. Though relatively few people are (54) them, red tides are not new.

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 (55) . A Philippines red tide expert told us that " (56) the fish kills, the Philippines has documented 1, 926 eases of dead shellfish poisoning caused by red tides. "

The term "red tide" (57) 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 (58) of brown or yellow. The World Book Encyclopedia reports that "the discolored areas may range from (59) a few square yards to more than 2,600 square kilometers. "

What causes such discoloration Red tides are generally caused by several species of single-celled organisms. These tiny organisms have hair-like projections which they use to (60) themselves in water.

51().

A. As a result

B. As it is

C. As expected

D. As usual