If s and t are subsets of real numbers, then which of the following relation holds for union? (a) (s u t) = s u t (b) (su t° = s° ut° (c) isolated point of (s t

If S and T are subsets of real numbers, then which of the following relation holds for union? (A) (S u T) = S U T (B) (Su T° = S° uT° (C) Isolated point of (S T) = Isolated point of S u lsolated point of T (D) Exterior point of (S T) = Exterior point of Su Exterior point of T A B C which option is correct