at once ,right now,right away和now的区别

(1) right away,at once 侧重动作,有多种时态,谓语动词随时态变化而变化.　I’ll return the book right away.我马上还书.Several things happened at once.几件事情同时发生.America should start its work at once...right away 表示“立即，马上，立刻”。同义词有：at once，immediately，通常与一般将来时和一般现在时连用