#### Answer

(a) positive
(b) positive
(c) negative
(d) positive

#### Work Step by Step

(a) Since b is negative, -b is positive
(b) Since b and c are negative, bc is positive. Since a is also positive, a + bc is the sum of positive numbers, which is positive.
(c) c is negative and a is positive, thus c-a is a negative number minus a positive number, which becomes a more negative number. Thus the result is negative.
(d) b is negative, so $b^2$ is positive (a negative number times itself is positive). a is positive, so $ab^2$ is the product of two positive numbers, which is also positive.