填空题
[听力原文]11-15
Many of the world’s people are concerned about the decreasing whales in the oceans and seas. People have hunted whales since about the eleventh century. Certain types of whales have been hunted too much. Recently, their numbers have decreased so much that they are in danger of disappearing.
Why do people want to save the whales The reason is that whales help to keep a balance between plants and animals. People have disturbed this balance. People’s wastes increase the amount of salt in ocean and seawater. The increased salt helps some plants and some very small animals to grow. These plants and animals can be harmful to fish. Whales eat enormous amounts of the plants and animals that live in very salty water. Therefore, whales are very important because they keep the ocean environment clean enough for fish.