What were you doing then?(then 可换成at that time吗?）它们能互换吗?

What were you doing then?(then 可换成at that time吗?）它们能互换吗? at that time等于什么?是等于then吗? Then,what are you doing 英语连词成句 doing do you that what you remember were at time at that time 和then的区别 you,then,can,doing,were,remember,what,you,) 连词成句 you,then,can,doing,were,remember,what,you,) 连词成句 急 what are you doing today then? What were you doing at this time yesterday morning? What were you doing at this time yesterday?怎么回答 by this time、by that time、at this（that?） time、since then 的区别 翻译中文：what were you think at that time