Assertion : Arthritis or inflammation of a joint makes the joint painful.
Reason : Some toxic substances are deposited at the joint

Options

A. (a) If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.
B. (b) If both Assertion and Reason are true, but the Reason is not the correct explanation of the Assertion.
C. (c) If Assertion is true, but Reason is false .
D. (d) If both Assertion and Reason are false.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that "Arthritis or inflammation of a joint makes the joint painful." This is a true statement. Arthritis is characterized by inflammation in the joints, which leads to pain, swelling, and redness.

2. **Analyzing the Reason**: The reason given is "Some toxic substances are deposited at the joint." This statement is misleading. While certain substances can accumulate in joints, the term "toxic substances" is not accurate in the context of arthritis.

3. **Identifying the Causes of Arthritis**: The pain associated with arthritis is primarily due to inflammation, which can result from various factors:
- Accumulation of uric acid (as seen in gout).
- Wear and tear of joint cartilage.
- Previous joint injuries.
- Autoimmune responses (e.g., rheumatoid arthritis).

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.

5. **Final Answer**: The correct option is C: Assertion is true, but the reason is false.