It's about ten years since I ____ in Australia.

问题描述:

It's about ten years since I ____ in Australia.
为什么用have been.一般我们初中常见的都是 现在完成时 + since + 过去的某个时间点...
所以不是很明白这句话,如果用arrived 为啥不行.
或者具体说一下since的用法

常见的:It has been about ten years since I arrived in Australia.所以用Arrived是正确的但是如果不用动词arrive,而用be,则要说since I have been ...原句里面的It's about ten years 严格地说应该是 It's been a...