If \(A \cap B = B\), then
(a) \(A\subseteq B\)
(b) \(B\subseteq A\)
(c) \(A=\Phi\)
(d) \(B=\Phi\)
Solution
\[ A\cap B=B \]
This means every element of \(B\) belongs to \(A\).
Therefore,
\[ B\subseteq A \]
Answer
\[ \boxed{B\subseteq A} \]
Correct option: (b)