Assertion : Cockroach shows sexual dimorphism
Reason : The female cockroach bears a pair of short thread like anal styles.

Options

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

Explanation

To analyze the given assertion and reason, we will break down the statements step by step.

### Step 1: Understand the Assertion
The assertion states that "Cockroach shows sexual dimorphism."
- **Sexual dimorphism** refers to the differences in appearance between males and females of the same species. In cockroaches, males and females do exhibit some morphological differences.

### Step 2: Understand the Reason
The reason provided is "The female cockroach bears a pair of short thread-like anal styles."
- This statement is incorrect because it is the male cockroach that possesses the anal styles, not the female. The female cockroach does not have these structures.

### Step 3: Evaluate the Truth of Each Statement
- **Assertion**: True, as cockroaches do show sexual dimorphism.
- **Reason**: False, as the female cockroach does not have anal styles; they are present in males.

### Step 4: Conclusion
Since the assertion is true and the reason is false, the correct answer is that the assertion is true but the reason is false.

### Final Answer
The correct option is: **Option 3 - Assertion is true but reason is false.**

---