The correct answer is option D: Shopkeeper.

The role of a shopkeeper is to sit in a shop and sell goods. Let's understand why the other options are not correct.

a) Fireman: A fireman is a person who is trained to extinguish fires and provide emergency services. They are not involved in selling goods in a shop.

b) Washerman: A washerman, also known as a laundryman or dhobi, is a person who washes clothes for a living. They do not sit in a shop and sell goods.

c) Policeman: A policeman, also known as a police officer, is responsible for maintaining law and order, preventing and detecting crimes, and ensuring the safety of the public. They do not typically sit in a shop and sell goods.

Now, let's discuss the role of a shopkeeper in more detail.

Role of a Shopkeeper:
1. Selling Goods: The primary role of a shopkeeper is to sell goods. They have a variety of products available in their shop, ranging from groceries, clothing, electronics, and more. They interact with customers, understand their requirements, and help them make purchases.

2. Managing Inventory: Shopkeepers are responsible for managing the inventory of their shop. They keep track of the stock, restock items when necessary, and ensure that the shop is well-stocked with products that customers demand.

3. Customer Service: Shopkeepers provide customer service by assisting customers in finding products, answering their queries, and providing recommendations. They aim to provide a positive shopping experience to customers and build customer loyalty.

4. Pricing and Billing: Shopkeepers set prices for the goods in their shop based on factors like cost, market demand, and competition. They also handle billing and ensure that customers are charged accurately for their purchases.

5. Maintaining the Shop: Shopkeepers are responsible for maintaining the cleanliness and organization of their shop. They arrange products on shelves, display them attractively, and keep the shop clean and tidy.

6. Handling Payments: Shopkeepers handle cash and other forms of payment from customers. They ensure that transactions are processed correctly and provide customers with receipts.

In conclusion, a shopkeeper is the correct answer to the question as they sit in a shop and sell goods. They play a crucial role in managing inventory, providing customer service, maintaining the shop, and handling payments.