Questions Such As: What Role Do Visual, Auditory, or Social

Questions such as: what role do visual, auditory, or social stimuli play in the emergence of a behavior? or, what happens when a behavior ceases to be part of the individual's behavioral repertoire? or, does a particular behavior always proceed in a predictable and reliable fashion among individuals in the species? are examples of which of Niko Tinbergen's four main types of questions that should be asked about behavior?

A) development.
B) evolution.
C) mechanism.
D) survival value.