Which part of an amino acid is the only one that varies and is what defines its properties

Although the two theories differ on the evolutionary path of dinosaurs, they agree that

Suppose you use three different scale to weigh a bag of organges. one scale says the nag weighs 2.1 lb, and third says it weighs 2.1 lb. the actual weight of the bag of organges is 2.153 lb. which of the following best decribes these results?

The offspring of a black cat and a white cat is a gray cat, it has the genotype bw if a black cat mates with a gray cat the chance that the offspring is white will be what percent?