Explanation:

- Excise Duty: This is an indirect tax charged on the manufacture of goods. It's paid by the manufacturer, but the cost is typically passed on to the consumer.

- Sales Tax: An indirect tax imposed on the sale of goods and services. It's collected by businesses and paid to the government.

- Both (a) and (b): Both excise duty and sales tax are forms of indirect taxes. They are charged at different stages of the product lifecycle, eventually affecting the consumer.

- Wealth Tax: This is a direct tax on an individual's net wealth. It's levied directly on the taxpayer based on their assets.

Correct Answer: Option 3 - Both (a) and (b)