Raw materials are an example of a firm's costs. answer
a. selling
b. operating
c. fixed
d. variable

d. variable

Explanation:

As the raw material are a direct cost to the company they are termed as a fixed cost as they are the assets of the production and consumption. But their availability is subject to a matter of use thus they are categorized as a variable cost to the resources of the company or firm. An example is that o the wood as a raw matter has to be produced as finished goods thus the amount of seasonal wood available for the construction activities to take place is another cost to the company. Hence the erw matter is seen as a variable cost.

A,b,c is the answer to the question