Morgan chose fruit files ( Drosophila melanogaster ) as the study model for his experiment. Certain reason made this organism suitable for the study . Which of the following is not one such reason ?

Options

A. They could be grown on simple synthetic medium in the laboratory .
B. They taken about 6 weeks to complete their life cycle .
C. A single mating could produce a large number of progeny files .
D. The male and female files are easily distinguishable .

Answer

To solve the question regarding why Morgan chose Drosophila melanogaster (fruit flies) for his experiments, we need to analyze the given options and identify which one is not a valid reason for their suitability as a study model.

### Step-by-Step Solution:

1. **Understand the Context**: Morgan used Drosophila melanogaster to study genetics and verify the chromosomal theory of inheritance. We need to identify the reasons that made fruit flies a suitable model organism.

2. **Evaluate Option A**: "They could be grown on simple synthetic medium in the laboratory."
- This statement is true. Drosophila can be easily cultured in a laboratory setting on simple media, making them convenient for genetic studies.

3. **Evaluate Option B**: "They took about six weeks to complete their life cycle."
- This statement is incorrect. Drosophila melanogaster typically completes its life cycle in about 1 to 2 weeks, not 6 weeks. Therefore, this option does not represent a valid reason for their selection.

4. **Evaluate Option C**: "A single mating could produce a large number of progeny flies."
- This statement is true. Drosophila are known for their high reproductive capacity, allowing researchers to obtain large numbers of offspring from a single mating.

5. **Evaluate Option D**: "The male and female flies are easily distinguishable."
- This statement is also true. Male and female Drosophila have distinct physical characteristics, which makes it easy for researchers to differentiate between them during experiments.

6. **Conclusion**: After evaluating all the options, it is clear that Option B is the statement that is not a valid reason for Morgan's choice of Drosophila melanogaster as a study model. Therefore, the answer is Option B.

### Final Answer:
**Option B**: They took about six weeks to complete their life cycle (this is incorrect).