Step 1: Understanding the Pie Chart
The pie chart shows that petrol expense accounts for 10% of the monthly salary.
Step 2: Calculating the Monthly Salary
Given that the petrol expense is Rs 500, which is 10% of the monthly salary:
\[
10\% \text{ of Salary} = 500 \implies \text{Salary} = \frac{500}{0.10} = 5000 \text{ Rs}.
\]
Step 3: Matching with the Options
The monthly salary is Rs 5,000, which corresponds to option (C).
Final Answer: The monthly salary is (C) 5,000.