The correct answer is $\boxed{\text{C}}$.
Prime cost is the direct costs of production. It is the sum of direct material cost and direct manufacturing labor cost.
In this case, direct material cost is $75,000 and direct manufacturing labor cost is $20,000. Therefore, prime cost is $75,000 + $20,000 = $95,000.
Option A is incorrect because it is the sum of direct material cost and indirect manufacturing labor cost. Indirect manufacturing labor cost is the labor cost that is not directly associated with the production of a product. It includes costs such as supervision, maintenance, and quality control.
Option B is incorrect because it is the average of direct material cost and direct manufacturing labor cost.
Option D is incorrect because it is the sum of direct material cost and direct manufacturing labor cost divided by 2.