The answer is A. Direct cost.
A direct cost is a cost that can be easily and conveniently identified with a particular unit of cost. For example, the cost of materials used to make a product is a direct cost, because it can be easily identified with the product.
An indirect cost is a cost that cannot be easily and conveniently identified with a particular unit of cost. For example, the cost of rent for a factory is an indirect cost, because it cannot be easily identified with any particular product.
Overhead is a general term for indirect costs.
I hope this helps! Let me know if you have any other questions.