Hirsch and McCauley's Selection in Flies for the Ability to Be

Hirsch and McCauley's selection in flies for the ability to be conditioned to extend their proboscis when water is applied to their feet demonstrated that:

A) A reflex cannot be conditioned but can be mated out of the population
B) Operant and respondent processes are separate and cannot be conditioned simultaneously
C) Conditioning of a reflex has a range of variability
D) An operant behavior can only be successfully conditioned in conjunction with a respondent behavior