Assertion:- The aquatic mammals like Dolphins whales etc. do not contain gill slits.
Reason : Their adaptation to aquatic life is secondary.

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.

Answer

To analyze the assertion and reason provided in the question, we can break it down into a step-by-step solution.

### Step 1: Understanding the Assertion
The assertion states that aquatic mammals like dolphins and whales do not contain gill slits. This is true because these mammals are air-breathing and possess lungs instead of gills, which are characteristic of fish.

**Hint:** Consider the respiratory systems of aquatic mammals compared to fish.

### Step 2: Understanding the Reason
The reason given is that their adaptation to aquatic life is secondary. This means that these mammals evolved from land-dwelling ancestors and adapted to life in water, which is indeed correct. Their ancestors had lungs, and over time, they adapted to an aquatic environment.

**Hint:** Think about the evolutionary history of mammals and how they transitioned from land to water.

### Step 3: Evaluating the Relationship
Now, we need to evaluate whether the reason provided is a correct explanation for the assertion. Since both the assertion and the reason are true, and the reason explains why aquatic mammals do not have gill slits (because they adapted from land mammals), this means that the reason is indeed a correct explanation of the assertion.

**Hint:** Reflect on how evolutionary adaptations can influence anatomical features.

### Step 4: Conclusion
Based on the analysis, both the assertion and the reason are true, and the reason correctly explains the assertion. Therefore, the correct option is that both assertion and reason are true, and the reason is the correct explanation of the assertion.

**Final Answer:** Both assertion and reason are true, and reason is the correct explanation of assertion.