When a fair die is thrown twice, let $(a, b)$ denote the outcome in which the first throw shows $a$ and the second shows $b$. Further, let $A, B$ and $C$ be the following events: $A=I(a, b) \mid a$ is odd $\}$. $B=\{(a, b) \mid b$ is odd $\}$ and $C=\{(a, b) \mid a+b$ is odd $\}$. Then
(a) $P(A \cap B)=1 / 4$
(b) $P(B \cap C)=1 / 4$
(c) $P(A \cap C)=1 / 4$
(d) $P(A \cap B \cap C)=0$