Ashton surveyed some of the employees at his company about their cell phone habits. from the data, he concluded that most employees at his company use cell phones primarily for business. for which sample could this generalization be valid?

a. all managers in the company
b. some managers and some sales executives selected at random
c. every fifth employee on the employee list
d. every other sales executive on the employee list

It can't be A. since if you only look at managers, you are missing all the sales executives.

It may be C. this option is more random but doesn't guarantee that you will represent both groups of employee's. Also, each time you would conduct the survey, you will receive the exact same results since it is the same people. 

It isn't D. for the exact same reason as A. but you're missing managers now. 

Therefore the answer is B. Some managers and some sales executives selected at random. This way you get a sample from both categories, and within those groups, it is randomly selected.

 I hope this helps!