Among the following physiological activities, what belongs to conditioned reflex is
A.
cough results from respiratory mucosa stimulation by secretions or foreigns
B.
blinking caused by foreigns touching the cornea
C.
the lower leg extension caused by tap quadrant tendon below the patella
D.
The limbs are painful and retract when hurt by harmful stimulation
E.
saliva secretion caused by smell the fragrance of food