If Z is a positive integer, which of the following must be odd?	Select:
A) x+1
B) Z^2+Z
C) Z^2+Z+1
D) x^2−1
E) 3x^2−3
A. Z+1 = can be odd or even. Since O + O =E or E + O = O   B. Z^2 + Z = Z(Z+1). Since from the above derivation we already know the term Z+1 can be Odd or Even, directly substitute here. Z(ODD) = Even (When Z is Even) or Z(EVEN) = EVEN [When Z is ODD]   C. Here's the answer. Since we know the term Z^2 + Z can always take a EVEN number, EVEN + 1 = ODD   Hence Z^2+Z+1.
<result>C</result>
If Z is a positive integer, which of the following must be odd?