Which of the following genetic crosses represents a test cross?

✅Explanation:
A test cross is a cross between an individual with a dominant phenotype (but unknown genotype) and a homozygous recessive individual. This is done to determine whether the dominant individual is homozygous (TT) or heterozygous (Tt).
The correct answer is (b) Tt x tt. In this cross, the individual with the dominant phenotype (Tt) is crossed with a homozygous recessive individual (tt). By observing the phenotypes of the offspring, we can deduce the genotype of the parent.

📌Other Options:
Tt x Tt: This is a monohybrid cross between two heterozygous individuals.
Tt x TT: This is a cross between a heterozygous individual and a homozygous dominant individual.
TT x tt: This is a cross between a homozygous dominant individual and a homozygous recessive individual.