If integers c and b are distinct factors of 30, which of the following CANNOT be a factor of 30?
I. cb + b^2
II. (c + b)^2
III. c + 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. cb + b^2 --&gt; if c=1 and b=2 then cb + b^2=6, which is a factor of 30. OK;   II. c + b)^2 --&gt; (c + b)^2 is a perfect square, no perfect square (but 1) is a factor of 30. DISCARD;   III. c + b --&gt; if c=1 and b=2 then c + b=3, which is a factor of 30. OK.   Answer: II only.
<result>B</result>
If integers c and b are distinct factors of 30, which of the following CANNOT be a factor of 30?
I. cb + b^2
II. (c + b)^2
III. c + b