To tell your father the truth is necessary 转换成用it 作形式主语还有几个：That the police keep order in an important football match is a hard job 转换成用it 作形式主语。I think it is important to master a foreign language 转换成用it 作形式宾语He felt that it was his duty to help the poor 转换成用it 作形式宾语I find that it's no good trying to persuade him转换成用it作形式宾语The football match had to be put off because of the bad weather 转换成对画线部分进行强调。because of the bad weather是画线部分

To tell your father the truth is necessary 转换成用it 作形式主语
还有几个：That the police keep order in an important football match is a hard job 转换成用it 作形式主语。
I think it is important to master a foreign language 转换成用it 作形式宾语
He felt that it was his duty to help the poor 转换成用it 作形式宾语
I find that it's no good trying to persuade him转换成用it作形式宾语
The football match had to be put off because of the bad weather 转换成对画线部分进行强调。because of the bad weather是画线部分