When two distributions are subtracted to form a new distribution, the new distribution must have a standard deviation of zero when which of A–E occur? (Choose all that apply.) 

A. The difference in the two standard deviations from the original distributions is zero. 

B. The difference in the two variances from the original distributions is zero. 

C. One or the other original distributions has a standard deviation of zero, but not both. 

D. Both original distributions have standard deviations of zero. 

E. Never. A standard deviation of a distribution can never be zero.