If integers w and b are distinct factors of 30, which of the following CANNOT be a factor of 30?
I. wb + b^2
II. (w+ b)^2
III. w + b
Select the correct option.
A) I only  B) II only  C) III only  D) I and II only  E) I, II, and III
Factors of 30 are: 1, 2, 3, 5, 6, 10, 15, and 30.   I. wb + b^2 --&gt; if w=1 and b=2 then wb + b^2=6, which is a factor of 30. OK;   II. (w + b)^2 --&gt; (w + b)^2 is a perfect square, no perfect square (but 1) is a factor of 30. DISCARD;   III. w + b --&gt; if w=1 and b=2 then w + b=3, which is a factor of 30. OK.   Answer: II only.
<result>B</result>
If integers w and b are distinct factors of 30, which of the following CANNOT be a factor of 30?
I. wb + b^2
II. (w+ b)^2
III. w + b