right now 和 at once 的区别?

at once right now at once ,right now,right away和now的区别 right now 和 at once 的区别? at once 和 right now 可以互相转换吗？ at the moment , at once,right now,right away区别用法和意思。 right away=at once=right now?right away和at once都是立刻的意思,而right now不是现在的意思吗? 请问right now和right away都是at once的同义词吗? at once 和right now ,now 词性是不是一样的?如题 either,also和too怎么区分?还有right now,at once怎么区分? at once right now right away at the moment 区别、比如用在哪个时态 he is doing homework___.A.right away B.right now C.at once D.immediately in no time,right away, right now, at once 有何差别,细讲 on the spots/at once/ right now/right away的区别 right now 的近义词 A just now B in a while C at once right now和at present分别是什么意思? at once的同义词是at the momeng或right now是吗? at once &right away区别, at once、right now等词可以用在过去式的句子中表示马上吗?