One of the best ways a business can keep labor costs down is to invest in:

A. It's products
B. It's customers
C. Its own stocks
D. It's employees

D. Its employees

The correct answer is D. It's employees.

Investing in employees can help a business keep labor costs down. By providing proper training and development programs, employees can become more skilled and efficient in their work, which can lead to increased productivity and decreased labor costs. Additionally, offering competitive wages and benefits can help attract and retain talented employees, reducing turnover and the need for costly recruiting and training processes. Additionally, investing in employee satisfaction and engagement can improve morale, which can also contribute to increased productivity and reduced labor costs.

To determine the correct answer, we need to understand the relationship between labor costs and the different options provided.

A. Investing in products: Investing in products may help improve the efficiency of the business, but it may not directly impact labor costs.

B. Investing in customers: While investing in customer satisfaction may lead to increased sales and revenue, it may not necessarily lower labor costs.

C. Investing in its own stocks: Investing in stocks has no direct impact on labor costs.

D. Investing in employees: Investing in employees can be an effective way for a business to keep labor costs down. By investing in training, employee development, and providing a positive work environment, businesses can improve employee productivity and reduce employee turnover. This not only helps in minimizing recruitment and training costs but also creates a more efficient and motivated workforce.

Therefore, the correct answer is D. Investing in its employees.