B
as soon as用法:
英语中的时态一般分为两种：现在时态,过去时态.
在时间状语从句中,主句用一般将来时,从句用一般现在时.
as soon as 一……就……,引导的就是时间状语从句；
I am going to watch TV as soon as I finish my homework.
在此句中,I am going to watch TV 就是一般将来时,I finish my homework这的finish是一般现在时.用finished 肯定不对.英语中的时态讲究主从句时态一致,除非从句所陈述的为客观事实或真理.如：
The teacher said the sun is bigger than the earth.
He is going as soon as he has had dinner.在此句中,he has had dinner为现在完成时,同样属于现在时态.