An online shopping site asks customers to rate the products they buy on a scale from 1 (strongly dislike) to 5 (strongly like). The invitation to rate a recent purchase is sent by email to customers one week after they purchase a product and customers can choose to ignore the invitation.

Which one of the given choices is the most important reason a confidence interval, based on the data from such ratings, has little use, for the mean rating by all customers who purchase a particular product?

A The customers who provide ratings cannot be considered a random sample from the population of all customers who purchase a particular product.

B. For some products, the number of customers who purchase the product is small, so the margin of error will be large.

C. The customers who provide ratings can be considered a random sample from the population of all customers who purchase a particular product.

D. Many of the customers may not read their email or a have spam filter that wrongly identifies the email requesting a review as spam.