I would have to say skin or hair
Because the mouth breaks down the food and the stomach uses acid to break food down even more...
Answer:a compound present in the body as a neurotransmitter and a precursor of other substances including epinephrine
Explanation:
SELECTIVE BREEDING INVOLVES CHOOSING PARENTS WITH PATICULAR CHARACTERISTICS TO BREED TOGETHER AND PRODUCE OFFSPRING WITH MORE DESIRABLE CHARACTERS . ... CROSS BREEDING INVOLVES TWO DIFFERENT BREEDS FROM THE SAME SPECIES TO CREATE A NEW BREED