I need the answers and a simple explanation, please :)

3. The main difference between saturated and unsaturated fatty acids is
(a) the amount of energy found in the fatty acid.
(b) saturated fatty acids are liquids.
(c) unsaturated fatty acids can be packed together very tightly.
(d) the number of hydrogen atoms bonded to the carbon atoms.

4. The function of proteins can include
(a) helping cells keep their shape.
(b) helping to destroy foreign substances.
(c) speeding up biochemical reactions.
(d) all of the above
bruoqmoo oinsgio

5. The characteristics of DNA includes which of the following?
(a) DNA is made of nucleotides consisting of a sugar, a phosphate group, and a carbon base
(b) DNA is made of a single polynucleotide chain, which winds into a double helix.
(c) DNA is how inherited characteristics are passed from one generation to the next.
(d) all of the above

6. Which category of organic compound is the major component of cell membranes?
(a) carbohydrate
(b) lipid
(c) protein
(d) nucleic acid

7. The cell wall of plants is made out of
(a) starch.
(b) glycogen
(c) cellulose
(d) chitin