(i) It can be seen that A⊂{0,1,2,3,4,5,6}B⊂{0,1,2,3,4,5,6}However, C⊂{0,1,2,3,4,5,6}Therefore, the set {0,1,2,3,4,5,6} cannot be the universal set for the sets A, B and C.(ii) A⊂ϕ,B⊂ϕ,C⊂ϕTherefore, ϕ cannot be the universal set for the sets A, B, and C.(iii) A⊂{0,1,2,3,4,5,6,7,8,9,10}B⊂ {0,1,2,3,4,5,6,7,8,9,10}C⊂ {0,1,2,3,4,5,6,7,8,9,10}Therefore, the set {0,1,2,3,4,5,6,7,8,9,10} is the universal set for the sets A, B and C.(iv) A⊂{1,2,3,4,5,6,7,8}B⊂ {1,2,3,4,5,6,7,8}However, C⊂{1,2,3,4,5,6,7,8}Therefore, the set {1,2,3,4,5,6,7,8} cannot be the universal set for the sets A, B, and C.