The correct option is A Conditioned reflex
An indifferent stimulus, combining with another stimulus capable of eliciting an unconditioned reflex, produces an unconditioned answer. After some time the indifferent stimulus is capable, by itself, to provoke an answer that can, then, be considered a conditioned one. Those indifferent stimulus can come from the external environment (auditory, olfactory, tactile and thermal stimuli) as well as from the internal environment (viscera, bones, joints). The conditioned responses can be the motor, secretory or neurovegetative. Voluntary or involuntary vegetative reactions can thus be conditioned. We can make those involuntary responses appear, at our will, if we use the appropriate conditioning. The conditioned responses can be excitatory (with function increase) or inhibitory (with function decrease).