Under all possible combinations which of the two friends will always have their room colours unchanged.
Explanation:
The following table can be made using the given 4 conditions :
Case 2a, 3a and 4a violates condition I, so these 3 cases are invalid.
Case 1a, 1b violates condition iii, so these cases are invalid.
Case 3b violates condition iv, so this case is invalid.
Finally we have the following two cases:
Nancy & Sunny.
Hence, option (c).
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