Let the random variable Q represent the number of students who go to a certain teacher's office hour each day. The standard deviation of Q is 2.2. Which of the following is the best interpretation of the standard deviation? А. On average, the number of students going to an office hour varies from the mean by about 2.2 students. B. For a randomly selected office hour, the number of students who will go is 2.2. C. For a randomly selected office hour, the number of students expected to go will vary from the mean by 2.2 students. D. For a random selection of office hours, the average number of students expected to go is 2.2. E. For a random selection of office hours, the E average number of students expected to go will vary from the mean by 2.2 students.