Assertion : The characteristics of cathode rays do not depend upon the material of electrodes and the nature of the gas present in the cathode ray tube.
Reason : Cathode rays consist of negatively charged particles, called electrons.

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 solve the question regarding the assertion and reason about cathode rays, we can break it down into a step-by-step analysis:

### Step 1: Understand the Assertion
The assertion states that "The characteristics of cathode rays do not depend upon the material of electrodes and the nature of the gas present in the cathode ray tube."

**Explanation**: This means that regardless of what materials are used for the electrodes or what gas is inside the cathode ray tube, the properties of the cathode rays (which are beams of electrons) remain the same.

### Step 2: Understand the Reason
The reason states that "Cathode rays consist of negatively charged particles, called electrons."

**Explanation**: This indicates that cathode rays are made up of electrons, which are negatively charged particles. This is a fundamental property of cathode rays.

### Step 3: Analyze the Relationship between Assertion and Reason
Now, we need to determine if the reason provided correctly explains the assertion.

- The assertion is true because all electrons have the same charge-to-mass ratio, regardless of the material of the electrodes or the type of gas present. Therefore, the characteristics of cathode rays remain unchanged.
- The reason is also true since cathode rays are indeed composed of electrons.

### Step 4: Determine if the Reason Explains the Assertion
While both the assertion and reason are true, the reason does not explain why the characteristics of cathode rays do not depend on the material of the electrodes or the nature of the gas. The reason simply states what cathode rays are made of, but it does not provide a direct explanation for the assertion.

### Conclusion
Both the assertion and reason are true, but the reason is not a correct explanation of the assertion. Therefore, the correct answer is: **Both assertion and reason are true, but reason is not the correct explanation of assertion.**

### Final Answer
The correct option is: **Option 2: Both assertion and reason are true, but reason is not the correct explanation of assertion.**

---