在學人教版八下的uint 3 吧
when 后面可以引導兩種從句
①時間狀語從句,后面可以是過去式,也可以是進行時
when 從句中的動詞可以延續(xù),也可以非延續(xù)
whicle 從句中動詞必須是可以延續(xù)的,從句多用進行時態(tài)
【注】如果從句中是延續(xù)性動詞,兩個可以互換
如：The students were talking when the teacher came in. -
（此時不能用 while 替換,因為 come是個非延續(xù)性動詞）
When the students were talking, the teacher came in.
While the students were talking, the teacher came in.
②賓語從句,
如果主句是現(xiàn)在時態(tài),從句可以用任何時態(tài)
如：I don't know when he will come.
如果主句是過去時態(tài),從句要用相應的過去時態(tài)
如：I didn't know when he came last week.
歡迎追問,滿意記得采納喲我在學七年級下冊。。。。