How many variables should be manipulated in a correctly performed scientific experiment

In a cross between individuals of a species of tropical fish, all of the male offspring have long tail fins, and none of the females possess the trait. mating two of the f1 fish fails to produce females with the trait. explain the inheritance pattern of the trait.

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?

Which rate indicates the number of children that would be born per women if she were to live to the end of her child-bearing years