If he comes bacK,please let me know.为什么不用If he will come back

If he comes bacK,please let me know.为什么不用If he will come back
If he comes bacK,please let me know.为什么不用If he will come back

If he comes bacK,please let me know.为什么不用If he will come back
if 是条件词 后面引导的语句要用一般现在时,不可以用将来时态,所以不用if he will come back