is the product of a and b odd?
(1) a has only 2 factors => a is a prime number. it could be 2 (even) or 3 (odd). +no information about b.
a could be 2 (even) or other prime # (odd). we would need to know if b is even or odd to answer the question.
this tells us that b is odd since 2 times any number (even or odd) will be even. add +1 to an even # and it will always be odd. we need to know if a is even or odd to answer the question.
down to answer choices c and e.
when combined, we know that a is 