爆爆简单

when I arrive at the airport这个是一般时态表将来

意思是“我将来到达机场的时候”当然要用将来时D will be waiting for

例如下列动词：come, go, arrive, leave, start, begin, return的一般现在时表将来。这主要用来表示在时间上已确定或安排好的事情。
The train leaves at six tomorrow morning.
When does the bus star? It stars in ten minutes.
用现在进行时表将来时(表示按计划安排要发生的事件。)

一般现在时表将来
一般现在时代替将来时

时间状语从句，条件句中，从句用一般现在时代替将来时
When, while, before, after, till, once, as soon as, so long as, by the time, if, in case (that), unless, even if, whether, the moment, the minute, the day, the year, immediately

He is going to visit her aunt the day he arrives in Beijing. 他一到北京，就去看他姨妈。

典型例题
(1）He said he________me a present unless I_______ in doing the experiment.
A. had not given; had not succeeded B. would not give; succeed
C. will not give; succeed D. would not give; will succeed.
答案B. 在时间，条件或让步主语从句中一般不用将来时。本题有He said，故为过去式。主句用将来时，故选B. 此处用一般过去式代替了过去将来时。