Final answer:
An individual with the genotype TtYy can produce four types of gametes: TY, Ty, tY, and ty.
Step-by-step explanation:
If an individual has the genotype TtYy, they can produce the following gametes: TY, Ty, tY, and ty. This variety of gametes is due to the law of independent assortment, which states that each allele separates independently of alleles for other genes, enabling the formation of gametes with all possible combinations of alleles provided by the parent. The correct answer to the question is, therefore, option D. This is similar to the gametes formed by an individual with the genotype AaBb, which are AB, Ab, aB, and ab.