Revision
1、Revise countries and languages
2、Review Grammar: noun clause and finish exercises on page. 28-29
Grammar： Empty subject “It” (形式主语)
1、“it” 在英语中是个很活跃的单词，有许多功能，作形式主语是其功能之一。用“It”作形式主语，主要是因为句子的真正主语较长，为了避免产生头重脚轻的现象才使用的。“It”作形式主语时，有一些惯用句式：
1) 当主语是主语从句时，常用句式：It + be + adj./ n. + 主语从句.
e.g. It is quite important that we study every subject well.
It is my duty that the lights are turned off when we leave the classroom.
It is still a question when and where we will have the meeting.
It’s strange that he should be late for the conference.
2) 当主语是不定式短语时，常用句式：It + be + adj. / n. + (for sb.) + to do sth.
e.g. It’s necessar y for us to obey the school rules.
It’s impossible for you to finish the work in two hours.
