5.It was not until 1874，when a young American explorer followed the Nile from Lake Victoria through to Lake Albert，that this part of the river’s course was finally explored.（强调句型）
6.It was believed that the northern coast of this continent lay somewhere in the Pacific Ocean.（It is/was
believed that...人们相信……）
Units 3－4
Ⅰ.重要词汇及短语
1.as a consequence（of ）作为（……的）结果
2.the Commonwealth of Australia 澳大利亚联邦
3.go walkabout到灌木丛中闲逛
4.break out（指激烈事件）突然发生
5.feed...on给（人或动物）食物；喂养；饲养
6.round up使集合在一起
7.stand for代表，代替；象征，意味着
8.have a strong/great influence on...对……有重大影响
9.benefit from...从……受益
10.differ from...和……不同
11.be fond of喜欢
12.have fun with开玩笑