Answer:
B. purchasing more machinery.
Explanation:
Marginal return can be defined as the return rate which a firm or a business experiences when they increase the amount of variable input that is been used in that firm or organisation.
It is important to note that all other input apart from the variable input remains constant.
Examples of variable inputs that a firm or organisation can increase
a. Purchase of more machinery
b. Increasing the amount of labour in the firm.
