A test cross is carried out to

Options

A. find the number of alleles of a gene
B. determine two species will breed successfully
C. Predict whether two traits are linked
D. determine the genotype of a plant in F2 generation.

Answer

To solve the question "A test cross is carried out to", we need to analyze the options provided and understand the concept of a test cross in genetics.

### Step-by-Step Solution:

1. **Understanding Test Cross**:
- A test cross is a genetic cross performed to determine the genotype of an individual exhibiting a dominant phenotype. This is done by crossing it with a homozygous recessive individual.

2. **Analyzing the Options**:
- **Option A**: "Find the number of alleles of a gene" - This is incorrect. A test cross does not determine the number of alleles; it focuses on genotype.
- **Option B**: "Determine two species will breed successfully" - This is also incorrect. A test cross does not assess species compatibility.
- **Option C**: "Predict whether two traits are linked" - This is not the purpose of a test cross. It does not predict linkage between traits.
- **Option D**: "Determine the genotype of a plant in F2 generation" - This is correct. A test cross helps to identify whether the dominant phenotype is homozygous dominant or heterozygous by analyzing the offspring's phenotypes.

3. **Conclusion**:
- The correct answer is **Option D**: A test cross is carried out to determine the genotype of a plant in the F2 generation.