Why is it important to evaluate increases and decreases in operating expenses?

(a) Increases in operating expenses may indicate inefficiencies, and decreases in operating expenses may be detrimental to long-term sales growth.

(b) It is important to determine whether companies are spending at least 10 cents of every sales dollar on advertising expenses.

(c) Increases in operating expenses are always an indication that a firm will increase sales in the future.

(d) None of the above.