Official solution
From the given conditions, we have :
A \cap B = A \cap C : The intersection of set A with set B is the same as the intersection of set A with set C. This indicates that all elements common to A and B are also common to A and C, and vice versa.
A \cup B = A \cup C : The union of set A with set B is the same as the union of set A with set C. This indicates that all elements in A, B, and C are the same.
From these two conditions, we can infer that set B is equal to set C because every element of B is also an element of C and vice versa. Hence, Option B : B = C is the correct answer.