Test cross is a cross between

Options

A. Hybrid `xx` Dominant parent (Tt`xx`TT)
B. Hybrid `xx`Recessive parent (Tt`xx`tt)
C. Hybrid `xx` Hybrid (Tt`xx`Tt)
D. All the above

Answer

### Step-by-Step Solution:

1. **Understanding Test Cross**: A test cross is a genetic cross used to determine the genotype of an organism with an unknown genotype. This is essential in genetics to understand whether the organism is homozygous or heterozygous for a particular trait.

2. **Identifying the Cross**: The test cross is specifically conducted between the organism with the unknown genotype and a homozygous recessive parent. The homozygous recessive parent is used because it can provide clear results based on the offspring's phenotypes.

3. **Purpose of Test Cross**: The main purpose of a test cross is to reveal the genotype of the organism in question. If the organism is homozygous dominant, all offspring will show the dominant trait. If it is heterozygous, approximately half of the offspring will show the dominant trait and half will show the recessive trait.

4. **Conclusion**: Therefore, the correct answer to the question "Test cross is a cross between" is:
- An organism with an unknown genotype and a homozygous recessive parent.

### Final Answer:
The test cross is a cross between an organism with an unknown genotype and a homozygous recessive parent.

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