Answer :

All except absence of diversity

If there were no diversity, then all organisms would be the same, and none would have an advantage over the other. Therefore, no traits would be more beneficial for survival, and none of the "less fit" organisms would be selected against.
The answer would be Absence of Diversity because without any kind of diversity, organisms would all look similar to each other, such as bacteria, which reproduce by binary fission from one parent, looking exactly the same as the parent.