To sleep eight hours a night is important.(改为同义句)______ _______ to sleep eight hours a night.

To sleep eight hours a night is important.(改为同义句)______ _______ to sleep eight hours a night.
To sleep eight hours a night is important.(改为同义句)
______ _______ to sleep eight hours a night.

To sleep eight hours a night is important.(改为同义句)______ _______ to sleep eight hours a night.
It's important to sleep eight hours a night.
It 是形式主语 真正的主语 是后面不定式 里面的

it's important