The Class Mark Is the _________, and It Is _________

The class mark is the _________, and it is _________.

A) total number of class intervals in a frequency distribution; usually between 5 and 15
B) range of the observed values; the difference between the max and min values
C) width of the class intervals; approximately equal to the range divided by the number of classes
D) midpoint of each class interval; geometric mean of the class interval endpoints
E) midpoint of each class interval; arithmetic mean of the class interval endpoints