I don‘t know whether I should tell him the bad mews

whether to tell

I don't know if I should tell him the bad news

if引导的虚拟条件句中如果有should,were,had时，可以把should,were,had提前，if省略，句子倒装。
should i tell

I don't know If I tell him the bad news.
这里的“if”和“whether”的意思一样，是“是否”的意思...