Final answer:
Direct labor refers to the wages or salaries paid to workers who are directly involved in the production process. The wages of assembly line personnel are an example of direct labor. Correct option is a.
Step-by-step explanation:
Direct labor refers to the wages or salaries paid to workers who are directly involved in the production process. They are responsible for the physical creation or assembly of a product.
In this case, the wages of assembly line personnel would be an example of direct labor as they are directly involved in the manufacturing process on the assembly line.