are you sure you have to?it is been very late..——Are you sure you have to?It's been very late.——I don't know ___ I can do it if not now 选项：where,why,when,how
问题描述：
are you sure you have to?it is been very late.
.——Are you sure you have to?It's been very late.——I don't know ___ I can do it if not now 选项：where,why,when,how
答
when
——你确定你现在必须要做么？已经很晚了！
——如果我现在不做我不知道什么时候才能做。
表示时间，用when。
答
.——Are you sure you have to? It's been very late.你确定你必须做？已经很晚了。
——I don't know _WHEN__ I can do it if not now 如果我现在不做，我不知道什么时候才能做了
答
when when
答
when
答
亲,答案选：how,表方式,意味“如何”.
理由：主句I don't know 后面的从句后半部分为：I can do it ,主谓宾齐全,
所以只能选择表示方式的how.
祝学习进步,请采纳,谢谢!