Unit 11
情态动词的不定式:
1.The ground must be just right - neither too wet nor too dry.it's best to plant trees in spring because it's warmer.
2.Make sure that it is straight.
3.Put the tree in the hole next to the stick so that it is straight.
4.Tie the tree to the top of the stick to keep it straight.
5.Forests help to keep water from running away,so drought does not often happen.
Lesson 42 的第一段.
Unit 12 是总复习单元
Unit 13 过去将来时 数词的读法
1.What is the population of France?
2.increase by
3.the increasing population
4.By the year 2010,it may be seven billion.
5.How much does it cost?
6.prefer to ...rather than ...
Unit 14 过去完成时
Unit 15 动词不定式