He is very young.Iam not sure ____he can finish the work alone or not.A .how B .that C .whether D .if
为什么不选D呀！短语有whether……or not,whether or not和if……or 有if……or not。whether或if均可表示“是否”的情况如下：引导宾语从句，例如
I wonder whether/if the news is true or not.