If A and B are two events such that P(A) $\neq$ 0 and P(B | A) = 1 . Then choose the correct answer.

Question

\[ \begin{array} (A)\: A \subset B \quad & (B)\: B \subset A \quad & (C)\: B = Ø \quad & (D) \: A = \phi \end{array} \]