x and y are positive integers. If xy + 4x is odd, then which of the following must be even?  Choose one
A) x	B) y	C) x + y	D) xy − x	E) y+4
Given that xy + 4x is odd, which means x(y+4) is odd.   Product of two nos. will be odd only if both the nos. are odd.   Hence x is odd, y+4 is also odd.   y+4 is odd means y is even. Answer will be y+4.
<result>E</result>
x and y are positive integers. If xy + 4x is odd, then which of the following must be even?