Given sets A = {1, 3, 5}, B = {2, 4, 6}, C = {0, 2, 4, 6, 8}, which of the following can be considered as universal set(s) of three sets A, B, C ?

(i) {0,1,2,3,4,5,6} (iii)ϕ

(iii) {0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10} (iv) {1, 2, 3, 4, 5, 6, 7, 8}

Consider U₁ = {0, 1, 2, 3, 4, 5, 6}

∴  U₁ is not a universal set for A, B, C.
Consider : U₂ = 
None of members of sets A, B, C are members of set U₂

∴ U₂ is not a universal set.
Consider  : U₃ = {0, 1, 3, 4, 5, 6, 7, 8, 9, 10}
Every member of sets A, B  and C is a member of set U_3. 
Hence U₃ = {0, 1, 3, 4, 5, 6, 7, 8, 9, 10} is a universal set for sets A, B, C.
Consider                    U₄ = {1, 2, 3, 4, 5, 6, 7, 8 }

∴  U₄  is not a universal set sets A, B and C.
Hence,  the universal set is U₃ = {0, 1, 3, 4, 5, 6, 7, 8, 9, 10}