There are 52 cards to choose from, and assuming the choice is made at
random the probability that it coincides with a previously selected card
(whatever the method of selection) there is only one way of being right, so
the required probability is 1/52.
Now if the person A is not selecting at random, and neither is person B, then
the probability of picking the right card can be considerably higher than 1/52.
(like asking someone to pick a number between 1 and 10, the frequencies
of the posibilities are not all equal, there are favoured numbers 3 and 7 come