“马上”的英文有很多：
at once; immediately; right away;right now
下面给出逐条解释以及例句：
immediately adv.立即，马上；直接地；紧接地
Would she leave immediately if something like this happens?
如果发生这样的事情她会马上离开吗？
at once adv.立即；一起；同时；立刻
I desire you to go at once.
我请求你现在马上就走。
right away 立刻，马上；就；当时
I'll have our housekeeper come right away.
我马上叫我们的管理人员来。
right now 立即；此刻，目前；此时
I'm not worried right now that that is an issue.
眼下，我不觉得这是个需要担心的问题。