搞懂意思就选得出来了
as soon as 一经...;立即...;一...就...
前后的时态得一致.
by the time ...到...的时候
By the time they get here,we'll have finished the work.
等他们到这里时,我们会已经把工作做完
since,(常用于现在完成时或过去完成时)
此后;从那时到现在
She left school three years ago and has worked as a nurse ever since.
她三年前毕业,从那时起便一直当护士.
after就是在什么之后
原句意思是我到车站的时候火车已经离开了.