A punnet square predicts a 9:3:3:1 ratio for phenotypes. Explain what that ratio means ...

The punnet square gives the frequency with which each phenotype is observed. In this case, the possible outcomes are 9 + 3 + 3 + 1 = 16, 9 members will have one phenotype, three members will have a second phenotype, three members will have a third phenotype and 1 individual will have a fourth phenotype.