please let me know if he comes 中的if不可用whether代替

please let me know if he comes 中的if不可用whether代替 please let me know if he ------------(come) tomorrow? I don't know if he_.if he _home,please let me know.(return). I wonder if he _____.if he ______,please let me know as soon If Mr Smith___back,please let me know. If he comes ,please let me know_____ _____ _____ _____(尽快) Let me know if he _____you again. 状语从句,主将从现原则：If he comes back,please let me know.如果他回来,请通知我,主 If you know when he will come,please let me know.(改写同义句) if you know when he will ccome,please let me know .改为同义句 Let me know whether you are coming.是什么从句?Let me know if you Let me know whether you love me.为什么用whether,而不用if?