Concept:Each draw is independent because the card is replaced.The probability of each colour is equal on every draw.Explanation:There are two equally likely ways to get different colours: red then black, or black then red.P(Red)=5226​=21​ and P(Black)=21​.Since the first card is replaced, the second draw is independent of the first.P(Red then Black)=21​×21​=41​.P(Black then Red)=21​×21​=41​.Therefore, required probability =41​+41​=21​.Answer:21​, i.e. Option A.