Question

A = {1, 3, 5, 7, 9}

Answer 1

The $\cap$ symbol means intersection, so everything that is in both sets, and the $\cup$ symbol means union, so the two sets combined.

$B \cup C = \{1, 2, 4, 5, 6, 7, 8, 9, 10\} = S$
$A \cap S= \{1, 5, 7, 9\}$

So the answer is A.