朗读课文《明天更辉煌》中的诗句，解释带点词语的意思。

你被迫离开母亲的怀抱，骨肉分离撕断肠。

①被迫：

②断肠：

组成细胞膜的主要成分是（）

C

    Rivers are one of our most important natural resources(资源). Many of the world's great cities are located on rivers, and almost every country has at least one river through it that plays an important part in the lives of its people.

    Since the beginning of history, people have used rivers for transportation. The longest one in the United States is the Mississippi. The lifeline of Egypt is the Nile. To the people of India, the Ganges is great, but it is also important for transportation. Ships can travel along it for a thousand miles. Other great rivers are the Congo in Africa and the Mekong in southeastern Asia. The greatest of all for navigation(航海), however, is the Amazon in Brazil. It is so wide and so deep that large ships can go about two thousand miles up it.

    Besides transportation, rivers give food, water to drink, water for crops, and chances for fun and recreation for the people who live along their banks. In order to increase the supply of water for crops, engineers sometimes build a dam(坝) across a river and let a lake form behind the dam. Then people can use the water not only to irrigate(灌溉) their fields but also to make electricity for their homes and industries.

    However, large cities and industries that are located on rivers often cause problems. As the cities grow in size and industries increase, the water in the rivers becomes polluted with chemicals and other materials. People are learning the importance, however, of doing more to keep their rivers clean if they want to enjoy the benefits of them.

勃列日涅夫在执政前期对赫鲁晓夫时期的政策进行了调整。他把经济改革的重点放在重工业上，其根本目的是

4+47=□