这两句话表达的意思有什么区别?
As soon as he has received his exam results,he will phone us.
As soon as he receives his exam results,he will phone us.
第一句是新概念英语课本上的原句
还有
By the time violence has broken out,it is too late.
By the time violence brakes out,it is too late.
这两句又有什么区别？