Which Behavior Is the Best Example of a "Reflex Action

Which behavior is the best example of a "reflex action" as described by René Descartes?

A) Sydney is given a set of crayons, and she immediately chooses the green crayon to complete her drawing.
B) Travis descends stairs, trips and almost falls, and then notices that his heart is pounding and his breathing rate has increased.
C) A dog sees a rabbit run under a fence and then rapidly tries to squeeze under the fence.
D) A squirrel walks across the top of a fence, jumps to and crosses a telephone wire, leaps to the top of a bird feeder, and then opens the latched door to gain access to the bird seed.