It is our duty to keep our classroom clean and tidy.中的It《our duty 》和 clean and tidy是什么成分

问题描述:

It is our duty to keep our classroom clean and tidy.中的It《our duty 》和 clean and tidy是什么成分

our duty 是真正的主语 ,前面那个it 是逻辑主语 .
to clean and tidy是表语 动词不定时作表语
还原后是:
our duty is to clean our classroom and tidy