英语时态提问：大哥大姐们帮我看看下面这句话的时态,搞不清楚了.
The inspector pointed out that on the morning of the murder,the 8 o'clock train did not run at all,as it had broken down at Ferngreen station and had been taken off the line.为什么：the 8 o'clock train did not run at all 不用过去完成时?为什么：as it had broken down at Ferngreen station and had been taken off the line.在主句使用一般过去时的情况下,从句使用过去完成时,主句和从句是同时发生的呀?