In To Kill A Mockingbird what question does Calpurnia tell scout to ask her father, saying that he can explain it better?

In Chapter 12, Scout asks Calpurnia, "What's rape, Cal?" (124).  The question is in reference to Tom Robinson being accused of raping Mayella Ewell.  Calpurnia's exact response to Scout's question is, "It's somethin' you'll have to ask Mr. Finch about. . . . He can explain it better than I can" (124).  She then immediately changes the subject by asking if the children are hungry.

The reason why Calpurnia responds this way is another matter.  Calpurnia, being the wonderful cook, caretaker, and mother-figure that she is, knows that this is a conversation that Scout should have with Atticus.  A violent crime like rape should not be discussed (and certainly not described) to any child by anyone other than her parents.  The intelligent Calpurnia also knows that something forbidden suddenly seems very interesting to curious children.  However, a growing child's stomach usually takes precedence over absolutely everything else.