The correct answer for this question is option 'C', which states that test cross in plants or in Drosophila involves crossing the F1 hybrid with a double recessive genotype. Let's explain this answer in detail.

Test cross is a breeding technique used to determine the genotype of an individual showing a dominant phenotype. It involves crossing the individual of interest (known as the test cross individual) with a homozygous recessive individual. By observing the phenotypes of the offspring, we can determine the genotype of the test cross individual.

In the case of plants or Drosophila, there are different types of crosses that can be performed. However, the test cross specifically involves crossing the F1 hybrid (the first generation offspring resulting from a cross between two different parental lines) with a double recessive genotype. This is done to determine the genotype of the F1 hybrid.

Let's break down the answer further:

1. Test Cross:
- Test cross is a breeding technique used to determine the genotype of an individual with a dominant phenotype.
- It involves crossing the individual of interest (test cross individual) with a homozygous recessive individual.

2. F1 Hybrid:
- The F1 hybrid is the first generation offspring resulting from a cross between two different parental lines.
- In this case, the F1 hybrid is the individual that needs to be tested.

3. Double Recessive Genotype:
- A double recessive genotype refers to an individual that carries two copies of the recessive allele for a particular trait.
- In a test cross, the F1 hybrid is crossed with a double recessive individual.

4. Purpose of the Test Cross:
- The purpose of the test cross is to determine the genotype of the F1 hybrid.
- If the F1 hybrid is heterozygous (carrying one copy of the dominant allele and one copy of the recessive allele), the test cross will result in a 1:1 ratio of phenotypes in the offspring.
- If the F1 hybrid is homozygous dominant (carrying two copies of the dominant allele), the test cross will result in all offspring showing the dominant phenotype.

In conclusion, the correct answer is option 'C', as the test cross in plants or in Drosophila involves crossing the F1 hybrid with a double recessive genotype. This is done to determine the genotype of the F1 hybrid and can help in understanding the inheritance pattern of a particular trait.

In some of the plants self Cross is not possible so we do test cross .it is done in order to identify the genotype of a hybrid since by looking at the phenotype one cannot determine genetic composition when the f1 generation arises violet colour is dominant whereas homozygous white is recessive according to figure 5.5 of ncert