The correct answer is: B. prime cost
Primary packing is an item of prime cost because it is a direct cost of production. It is the cost of the materials and labor used to package the product.
Selling overheads are indirect costs of production that are incurred in the selling and distribution of the product.
Distribution overheads are indirect costs of production that are incurred in the distribution of the product to customers.
Factory overheads are indirect costs of production that are incurred in the factory, such as the cost of plant and equipment depreciation, factory rent, and factory insurance.