大学英语：S.+V.+it+adj.+to do sth.

　　1. S.+V.+it+adj.+to do sth. 形式宾语句型 n.

　　e.g. Some people find it difficult to succeed in language learning.

　　Some people find it difficult to succeed in other fields.

　　They find it easy to practice using the language regularly.

　　2. It is +adj.+for sb.+to do sth. 形式主语句型

　　e.g. It is more important for them to learn to think in the language than to know the meaning of every word.

　　It is necessary for them to learn the language in order to communicate with these people and to learn for them.