为什么是be fast asleep 而不是be fastly asleep?

为什么是be fast asleep 而不是be fastly asleep? be fast asleep和 be wide awake fast asleep/sound asleep be fast asleep与fall asleep的区别.顺便分别造句来说明他们的不同. fast fall asleep/ fall fast asleep 哪个对? fast fall asleep/ fall fast asleep 哪个对?有助于回答者给出准确的答案 she was still fast asleep,with her head buried deep into her arms为何用buried,如何翻译 fast=soundly,那么在具体的句子中,the girl is fast asleep.中fast 为什么是my heart beat fast而不是my heart jump fast.求详解 I fall ___ asleep.为什么要填fast 而不是quickly he was fast asleep on the back seat,翻译 be asleep 、be awake （中文） The girl is fast asleep.( 这个姑娘在酣睡）中的fast表示神魔意思 I----------just-----------(fall)asleep when I heard someone knocking at the door为什么是was falling啊,fall asleep不是短暂性动词吗? 什么是顺势而为 The girl is fast asleep.在句中fast是什么意思,soundly是什么意思,fast能否用soundly来替换 fasten为什么是固定的意思,fast不是快么?这意思是怎么变得,词根不是fast么? 解释下面词组pretend to be asleep