1 .
Let $A$ and $B$ be two events in some sample space. You are given that
$$
\begin{align}
\Pr(A|B) &= \Pr(B|A), \\
\Pr(A \cup B) &= 1, \\
\Pr(A \cap B) &> 0.
\end{align}
$$
Which of the following is true?
(a)
$\Pr(A) > 1/2$
(b)
$\Pr(A) > 0$
(c)
$\Pr(A) < 1$
(d)
$\Pr(A) < 1/2$