know 后面跟的是一個(gè)賓語(yǔ)從句,know (that) handing in homework on time is necessary.
handing in homework 用動(dòng)名詞做主語(yǔ)表示交作業(yè)這件事,to do 是交作業(yè)這個(gè)動(dòng)作但是賓語(yǔ)從句中that后加to do不是也可以嗎?大部分情況是主語(yǔ)或賓語(yǔ)太長(zhǎng)，前面用it這個(gè)形式主語(yǔ)或形式賓語(yǔ)，后面用to do sth 引導(dǎo)出真正的主語(yǔ)或賓語(yǔ)例如：It is important to hand in homework on time.All the students know it is necessary to hand in homework on time.我的理解是這樣的哈。