The filled-in squares of a Punnett square represent

a the numbers of individuals with each version of a trait.

b all possible combinations of gametes based on a cross between the two parents

c an exact ratio that must always occur when the same parents have 4 offspring.

dd examples of some of the offspring that can arise from a one-trait cross.

The answer is B. even if you fill out a Punnett Square there is still a possibility that it won't come out that way. for example there could be two dominant traits in a Punnett square instead of just one completely dominant trait. like BB and BB.

b all possible combinations of gametes based on a cross between the two parents

Explanation:

The square of punnet is a visual representation of the possibilities for a certain trait of the offspring of two individuals to manifest certain genes, based on the gamete genes of the parents, you create a square that shows all possible combinations of those gametes in order to calculate the probability of a certain gamete being showed in the offspring.