What type of costs are included in the operating expense category?

In the context of operating expenses within the hospitality industry, the correct choice reflects the categories of costs that are directly associated with the day-to-day functioning of hotel housekeeping operations. The cost of guest supplies and cleaning supplies falls under operating expenses because these are essential resources for maintaining the cleanliness and comfort of guest rooms and public areas.

Guest supplies, such as toiletries and linens, are necessary to enhance the guest experience, making them a recurring expense that impacts the overall budget of the housekeeping department. Similarly, cleaning supplies, including detergents, disinfectants, and equipment, are vital for the upkeep of the property and ensuring that sanitation standards are met. Together, these costs are fundamental to the operation of housekeeping and contribute significantly to the establishment's overall operational efficiency and quality of service.

While labor costs, utility expenses, and marketing expenses are also crucial for hotel operations, they do not specifically reflect the direct costs associated with housekeeping functions as highlighted in the correct answer. Labor costs pertain to staffing and wages, utility costs involve overhead expenses related to electric, water, and gas consumption, and marketing is focused on promotion and sales, which are separate from the day-to-day operational costs laid out in the context of housekeeping.