D is the only viable answer among these, as A, B, and C all contain two even integers which, by definition, have a greatest common factor of 2.
<em>Correction: </em>I was incorrect in saying that <em>all </em>even integers have a greatest common factor of 2; 2 is at least guaranteed to be <em>one of the common factors </em>in any group of even numbers, but these examples all have it as their <em>greatest </em>common factor as well.
