Choose a number and continuously add a constant to form a sequence with an even number of elements. Which of the following lists all the true statements about the sequence?

I. The mean is equal to the median.

II. The mode is equal to the median.

III. The mean is equal to the average of the 

smallest and largest number in the set.

A. I only

B. II only

C. I and II

D. I and III

E. I, II, and III