E(Y X1, ..., Xk. = Pr(Y = 1 X1,..., Xk. means that

A、 for a binary variable model, the predicted value from the population regression is the probability that Y=1, given X.
B、 dividing Y by the X's is the same as the probability of Y being the inverse of the sum of the X's.
C、 the exponential of Y is the same as the probability of Y happening.
D、 you are pretty certain that Y takes on a value of 1 given the X's.