Final answer:
The disadvantage of mall-intercept interviewing is that mall shoppers may not be representative of the target market population.
Step-by-step explanation:
The disadvantage of mall-intercept interviewing is that mall shoppers may not be representative of the target market population (option C). This means that the sample of shoppers being interviewed may not accurately reflect the larger population from which they are drawn. For example, if the target market population consists of a diverse range of age groups, income levels, and interests, but the mall shoppers being interviewed are predominantly young and affluent, the results may not be generalizable to the larger population.