Although instinct enables organisms to make complex responses to stimuli, instinctual behavior involves no reasoning and requires far fewer nerve cells than does noninstinctual (also called flexible) behavior. A brain mechanism capable of flexible behavior must have a large number of neurons, and no insect brain has yet reached a size capable of providing a sufficiently large number of neurons. Which one of the following can be properly inferred from the statements above?
A: All organisms with large brains are biologically equipped for flexible behavior.
B: Only organisms with brains of insect size or smaller engage in purely instinctual behavior.
C: Insect behavior is exclusively instinctual.
D: All organisms with brains larger than insects' brains are capable of some measure of flexible behavior.
Choose A, B, C or D as your solution.
C