Using the counting principle to determine the number of elements in the sample space. Two digits are selected with replacement from the digits 1,2,3,4

Sample space = {1,2,3,4} = 4 possible outcomes

(I guess you are asked to find the probability, if not do complete your question)

If so, then

Any 2 digits selected from the sample space with replacement its

Probability is P (any 2 digits) = 2/4 = 1/2 = 0.5