The two strangers are talking warmingly as if they___been friends for years为什么选had?

The two strangers are talking warmingly as if they___been friends for years为什么选had?
The two strangers are talking warmingly as if they___been friends for years
为什么选had?

The two strangers are talking warmingly as if they___been friends for years为什么选had?
been和for years可以看出这个句子应用完成时
而这是if引导的虚拟语气,虚拟语气一般用过去时
所以这个句子用过去完成时
即had done

as if 后面是假设的，假设句子
这两个陌生人正热情的交谈，好像他们是多年的朋友