For a Given Level of Expenditure,there Is No Way of Determining

For a given level of expenditure,there is no way of determining the mathematical optimum allocation between advertising and promotion because _____.

A) advertising and promotions are somewhat interchangeable
B) advertising and promotions produce a synergistic effect
C) advertising is appropriate for early stages of the product life cycle, and promotion is more appropriate during later stages
D) they are somewhat interchangeable and produce a synergistic effect
E) None of these are correct.