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.

yes? sounds right, but you didn’t ask a question.

"1. it should be, it has been for about 20 years, and it's really not much different in the end than breeding animals to have particular traits. there are always concerns about genetically engineered animals/plants affecting the environment in unexpected negative ways, but i can't think of an example where the fears didn't turn out to be baseless.  

first, as you point out, it would be a great advance in pharmacology, to be able to tailor drugs and their doses to me. the pros involve better medical treatment. the cons involve privacy issues like insurance companies denying coverage to people with genetic risk factors. looking at dna markers wouldn't affect the frequency of genetic diseases, but it would allow detection of them earlier. and ok, actually i suppose that if people used this information to avoid having children with genetic diseases, some might decrease in frequency."