除了第一个 (not a little),其他三个基本上没有区别,即 “无所谓”,或 “没关系”.
Mary:Do you mind if I have a sip of your coffee?
Mike:Not a bit/not at all/ not in the slightest.
Not a little 意思有点不同,一般来说这词语很常有 ”a lot" ,"big","plenty" 等意思.如
I met my cousin for the first time after a long absence.To my utter amazement she was not a little girl any longer.