Here we have 10 Contestants divided into 3 Teams:
Red -> 5
Blue -> 3
Green ->2
The desired probability is what is the probability that 4 choices of the selected rounds are not made up exactly of 2 from Team Red and 2 from Team Blue.
We can re-phrase the Probability as 1 - [2 Nos. of Candidates selected exactly from Team Red and Team Blue]. Remember doing this at the end else you'll be caught by the trick in the question.
Now coming to the candidates selected exactly from Team Red and Team Blue:
Total Outcomes Over all 4 Rounds = 10C1 X 10C1 X 10C1 X 10C1 = 10,000
Generally Probability = Favourable Outcomes / Total Outcomes
In this case it is, 1 - [Favourable / Total Outcomes], because we need to find the probability of NOT being from the selection.
Anyway, Favourable Outcomes is:
No. of Rounds in which the two teams are required:
4 Rounds; Each Round needs Red / Blue so something like RRBB or RBRB or BRBR or BBRR..... and so on.
The total number of these combinations are 4C2.
And the selection in each Round can be done in 5C1 X 5C1 X 3C1 X 3C1 no matter in which order they are ultimately arranged in each Round. If 2 are Red, the other 2 are automatically blue.
Hence the favourable outcomes are 4C2 X 5C1 X 5C1 X 3C1 X 3C1 = 1,350 Outcomes
Hence Probability = 1 - [1,350 / 10,000] = 1 - [27/200] = 173/200 => Option D is the answer.