To be happy,it's very important to have a good attitude and a good heart.改成

问题描述:

To be happy,it's very important to have a good attitude and a good heart.改成
To be happy,it is ___ ____ ____ to have a good attitude and a good heart.

of great impotance
be of +抽象名词 相当于 be +形容词 表示的意思,如:be valuable =be of great value