Question

8．学好一门外语对我们的未来发展非常有用．
It is very useful for our future development to learn a foreign language well．

Answer 1

分析 It is very useful for our future development to learn．

解答 答案：It is very useful for our future development to learn．结合句意这里是说客观事实用一般现在时，表示对某人来说做某事是怎样的用It's adj+for+sb to do sth，it是形式主语，动词不定式是真正主语，useful形容词有用的，我们的未来发展our future development，学习learn，故答案是It is very useful for our future development to learn．

点评 It's adj+for+sb to do sth．it是形式主语，动词不定式是真正主语，for前面的形容词是指某人做某事的性质，强调的是事．比如说，It's good for us to exercise more．
而如果是It's adj+of+sb to do sth，其中of前面的形容词则是做事的这个人的品格．比如说I's kind of him to help us．