On the number line shown, a is less than 0, which means a is a negative number, while b is greater than 0 which means b is positive. Therefore;
(A) ab (that is a times b) = negative ab
(B) -(ab) = positive ab (observe that ab is already a negative value)
(C) 2a - b = negative (observe that 2a gives a negative result, hence subtracting 3 from a negative number will resut in a negative answer)