Step 1: Meaning of honorarium.
Honorarium = payment made to someone (like Secretary, Treasurer) for services voluntarily rendered to the organisation.
Step 2: Nature of expense.
It is recurring in nature and is part of day-to-day operations → hence, it is a revenue expenditure.
Step 3: Eliminate wrong options.
- Capital expenditure → creates asset, not applicable.
- An income → completely wrong.
- All of these → cannot be correct as it is specifically a revenue expenditure.
Final Answer:
\[
\boxed{\text{Revenue expenditure}}
\]