Extracted text: Let X = {a, b, c, d} and T = { X, p, {a,b}, %3D {c,d}}, then An open proper subset of X may be clopen and may be not. Every open subset of X is clopen An open proper subset of X cannot be clopen O None of the choices O O
Extracted text: Let X = {1, 2, 3, 4, 5, 6} and let T1 = {X, p, {3}, {1,2,3}, {2,3,4}, {2}} and T2 = {X, ¢, {2}, %3D {1,2,3}, {4,5,6}, {2,4,5,6}} * T1 is a topology on X and T2 is not a topology on X T1 and T2 are both not topologies on X O T1 and T2 are both topologies on X T1 is not a topology and T2 is a topology on X