Assertion : Down syndrome, Klinfelter syndrome and Turner syndrome are chromosomal disorders.
Reason : In Klinfelter syndrome females are sterile.

Options

A. Both assertion and reason are true and reason is the correct explanation of assertion.
B. Both assertion and reason are true but reason is not the correct explanation of assertion.
C. Assertion is true but reason is false.
D. Both assertion and reason are false.

Answer

To solve the given question, we will analyze the assertion and reason step by step.

### Step 1: Analyze the Assertion
The assertion states that "Down syndrome, Klinefelter syndrome, and Turner syndrome are chromosomal disorders."

- **Down Syndrome**: This is caused by an extra copy of chromosome 21, leading to a total of 47 chromosomes (Trisomy 21).
- **Klinefelter Syndrome**: This occurs in males who have an extra X chromosome, resulting in a total of 47 chromosomes (XXY).
- **Turner Syndrome**: This affects females who have only one X chromosome, leading to a total of 45 chromosomes (X0).

Since all three conditions are related to abnormalities in chromosome number or structure, the assertion is **true**.

### Step 2: Analyze the Reason
The reason states that "In Klinefelter syndrome females are sterile."

- Klinefelter syndrome specifically affects males, not females. Males with Klinefelter syndrome often have reduced fertility or may be sterile due to the presence of an extra X chromosome. Therefore, the statement about females being sterile in Klinefelter syndrome is **false**.

### Step 3: Conclusion
Based on the analysis:
- The assertion is true.
- The reason is false.

Thus, the correct answer is: **Assertion is true but reason is false**.

### Final Answer
The third option is the correct answer.

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