he expained it to students that he was ill that day为什么explained后面要加it?

问题描述:

he expained it to students that he was ill that day
为什么explained后面要加it?

it指代这件事

it 是充当expain的谓语,that he was ill that day是it所指的内容,由于谓语太长就移到后面.