题目

        Dolphins（海豚）are not fish, but warm-blooded animals. They live in groups, and speak to each other in their own language. In this, they are like other animals, such as bees and birds. But dolphins are very different from almost all land animals. Their brain is nearly the same size as our own, and they live a long time―at least twenty or thirty years. Like some animals, dolphins use sound to help them find their way around. They also make these sounds to talk to each other and to help them find food. We now know they do not use their ears to receive these sounds, b阅读图文资料，完成下列要求。巴拉那河流量居南美洲第二，其河床基岩主要为坚硬的玄武岩，中上游瀑布密布，下游地势低洼。流经巴西与巴拉圭两国边境河段落差达150m，建于此处的伊泰普水电站为世界第二大电站，成为当地著名景点，所发电量由巴西与巴拉圭两国均分。下图为巴拉那河流域图。(1)分析巴拉那河下游沼泽的形成原因。(2)简析巴拉那河上游修建伊泰普水电站的有利条件。(3)简述修建伊泰普水电站的经济效益。(4)简述修建伊泰普水电站的不利影响。