【题目】—Why on earth didn’t you answer the door？I thought you were out this morning.
—I’m terribly sorry，but I online with my brother in America.
A. am chatting B. was chatting
C. chatted D. have been chatting
在线课程【答案】B
【解析】根据语境可知，答语意为“很抱歉，但我当时正在和在美国的弟弟网聊”，此处描述的是过去某个时刻正在进行的动作，故用过去进行时。故选B。