有关虚拟语气的问题

问题描述:

有关虚拟语气的问题
noisy as it was,he went on reading as if nothing___(happen)
为什么答案是were happening而不是had happened?
这两个不都是虚拟语气吗?

as if 虚拟时,把谓语时态往无as if 时前推一个时间段.比如无as if 用are,有以后用were.无as if 用have happened,有以后用had happened.无as if 用will go,有以后用would go.这里说他持续学习,是一个状态,无as if 时...