Answer:b. After three generations of breeding the smallest dogs, the average size of pups in a litter decreases by 3 pounds. -- Evolution
Explanation:Evolution refers to changes in inherited traits which occurs over successive generations.
These are genetical traits which are passed from parents to offsprings.
It may be due to mutation or combination of genes that causes genetical variations over time.
It is also driven by natural selection in which subjects with resistant genes stay long and have these passed from generation to generation or resulting to some genes being eliminated.