The reporter said that the UFO ________east to west when he

The reporter said that the UFO ________east to west when he saw it.
A．was travelling B．travelled
C．had been traveling D．was to travel.
我觉得我两种想法——
一、when he saw it 为时间状语从句
那么记者说的话为【the UFO is travelling east to west.】则选A.
二、when he saw it 与 the UFO was travelling east to west 是连起来的
即 the UFO was travelling east to west when he saw it.
根据直接引语变间接引语要将时态推后一格应该改成过去完成进行时
那不就应该选C了吗?但是答案是A啊.