A CEO leads a company of 250 employees and wants to conduct a survey. Which method would be a valid way to choose a random sample of 50 employees?

A. Go to the cafeteria and ask for 50 volunteers to complete the survey.

B. On a random workday, select the first 50 employees to arrive at the office to complete the survey.

C. Choose a department at random and survey 50 of the employees of that department.

D. Create a list of employees numbered 1 through 250. Use a random number generator to select 50 random numbers from 1 to 250 that represent the members to survey.