Can the complement of a context-free language be regular? I know that the context-free language is not closed under the complement , 
and the result could be context-free language or non-context free language
but my question is :

is it possible of the complement of context-free language = regular language ?
Since regular languages are all context-free and REG is closed against complement, every regular language is such an example.

As for non-regular context-free languages, the same closure property with a sprinkle of proof by contradiction easily shows that none of them can have a regular complement.