If x, y, and z are 3 different prime numbers, which of the following CANNOT be a multiple of any of x, y, and z?  Choose the correct choice from the following options
A) x + y  B) y – z  C) xy + 1  D) xyz + 1  E) x^2 + y^2
xyz and xyx+1 are are consecutive integers. Two consecutive integers are co-prime, which means that they don't share ANY common factor but 1. For example 20 and 21 are consecutive integers, thus only common factor they share is 1.   Since xyz is a multiple of each x, y, and z, then xyx+1 cannot be a multiple of any of them.   Answer: xyz + 1.
<result>D</result>
If x, y, and z are 3 different prime numbers, which of the following CANNOT be a multiple of any of x, y, and z?