Final answer:
The pair {A,C} forms a partition of X(option B).
Step-by-step explanation:
To determine which pairs of subsets form a partition of X, we need to understand the concept of a partition. A partition of a set is a collection of subsets that are non-empty, mutually exclusive, and their union is equal to the original set.
Let's analyze each pair of subsets:
(A) {A,B}: The subsets A and B have elements in common, so they are not mutually exclusive. Therefore, this pair does not form a partition of X.
(B) {A,C}: The subsets A and C do not have any elements in common, so they are mutually exclusive. Their union, {a,b,c,1,2,3}, equals X. Therefore, this pair forms a partition of X.
(C) {B,C}: The subsets B and C have elements in common, so they are not mutually exclusive. Therefore, this pair does not form a partition of X.
(D) {A,B,C}: The subsets A, B, and C have some elements in common, so they are not mutually exclusive. Therefore, this pair does not form a partition of X.
Based on the analysis, the correct pairs that form a partition of X are: (B) {A,C}.