1.that引导定语从句,指人或物,作宾语时可以省略.

    Do you know the man that is talking to your mother?

    Please show me the photos ﹝that﹞ you took last week.

    This is the museum﹝ that ﹞they visited last month.

2.that引导宾语从句,在口语或非正式文体中可以省略.

    He said ﹝that﹞he had finished the work by himself.

    He told me that was his usual way to deal with problems.﹝这里that做主语,不可省略﹞

    He suggested that we should keep on trying.

3.that引导主语从句,多用it做形式主语.

    It was clear that most students' hopes were the same.

    It is known to all that Mr Wang will give us a talk tomorrow.

    It is said that this book has been translated into several foreign languages.

4.that引导同位语从句,

    We are surprised at the fact that the children did it on their own.

    They expressed their hope that they would like to go to visit the Great Wall.

5.that引导表语从句,

    It seems that it is more difficult  for women to get a job  than men.

6.that用于强调句型中,

    It was on July 30 that they decided to meet again.

    It was in this old house that the police caught the two robbers.

7.that与so/such连用引导结果状语从句,

    He ran so fast that they all couldn't catch up with him.

    Mr Li is such a good teacher that all the students like him.

8.so that引导目的状语从句,

    Mr Wang got up very early this morning so that he could catch the early bus.