Which of the following economists has termed fixed cost as complementary cost?

The correct answer is: None of these.

Fixed costs are costs that do not change with the level of production. They are incurred regardless of whether the firm produces anything or not. Some examples of fixed costs include rent, insurance, and depreciation.

Complementary costs are costs that are incurred in conjunction with other costs. For example, the cost of hiring a worker is a complementary cost to the cost of providing them with tools and equipment.

Marshall, Prof. Ben, and Prof. Sen are all economists, but none of them have termed fixed costs as complementary costs.