wether和if不是表示原因吗,为什么引导宾语从句

if或whether在引导宾语从句中作“是否”讲,常用在ask,care,wonder,know,等动词后引出带有疑问意义的宾语从句.从句语序保持陈述语序,if或whether不充当成分,只起连接作用,不可省.

例I worry about whether I hurt her feeling.

例句

I\'m not sure whether I should tell you this.

我拿不准该不该把这事告诉你。

She asked her boss whether she could have the day off.

她问老板可不可以让她请一天假。

only time will tell if the treatment has been successful.

只有时间才能证明这种疗法是否成功。

It remains to be seen whether his project will fly.

他的计划能否成功尚需拭目以待。