Three of the following four number-pairs are alike in a certain way and one is different. Find the odd one out.

Observe the relation between the two numbers of every pair.

Case 1: Pair $$56 : 11$$
Sum of the digits of $$56$$ is $$5 + 6 = 11$$, which equals the second number.

Case 2: Pair $$78 : 13$$
Sum of the digits of $$78$$ is $$7 + 8 = 15$$, while the second number is $$13$$. The equality does not hold here.

Case 3: Pair $$12 : 3$$
Sum of the digits of $$12$$ is $$1 + 2 = 3$$, which matches the second number.

Case 4: Pair $$34 : 7$$
Sum of the digits of $$34$$ is $$3 + 4 = 7$$, again matching the second number.

Thus, in three pairs (A, C and D) the second number equals the sum of the digits of the first number, whereas pair B breaks this rule.

Option B which is: 78 : 13