3. an animal that relies on a digestive tract for digestion breaks down food by (1 point) a) intracellular digestion only. b) extracellular digestion only. c) both intracellular and extracellular digestion. d) neither intracellular nor extracellular digestion.

b) extracellular digestion only.

Explanation:

By extra cellular we mean to say that the digestion does not take place inside a cell. The digestion takes place in the lumen of alimetary canal instead. The alimentary canal is same as digestive tract. In small intestine which is a part of alimentary canal, the enzymes secreted by various glands help in the breakdown of complex food materials like carbohydrates, proteins, lipids etc. into simpler food materials like glucose, amino acids, glycerol & fatty etc. respectively. The reason why the complex food materials are broken down into simpler and smaller food materials is because complex food materials are bigger in size so they are unable to enter the blood vessels. After breakdown when they become small in size and they can easily enter the blood vessels. With the help of blood vessels they are transported to all the living tissues/cells of the body.