If X and Y are random variables,the sum of all the conditional probabilities of X given a specific value of Y will always be:

A) 0.0
B) 1.0
C) the average of the possible values of X.
D) the average of the possible values of Y.

The sum of all the conditional probabilities of X given a specific value of Y must always equal 1. This is because, given a specific Y value, there is a 100% chance that X will have some value. Therefore, the sum of all the probabilities of X given Y must equal 1.