Mary told me that she _____in the chemical for two more moths before quitting.A had worked B woulsd work C had been working D must have worked .老师给的答案是选B为什么不选A

Mary told me that she _____in the chemical for two more moths before quitting.A had worked B woulsd work C had been working D must have worked .老师给的答案是选B为什么不选A
Mary told me that she _____in the chemical for two more moths before quitting.
A had worked B woulsd work C had been working D must have worked .老师给的答案是选B为什么不选A

Mary told me that she _____in the chemical for two more moths before quitting.A had worked B woulsd work C had been working D must have worked .老师给的答案是选B为什么不选A
two more moths表示他还要再努力两个月,主句是过去时,所以是过去的将来would work