Randomization in an experiment

#1
Hi, everyone. I know randomization is basically to help guarantee that the experiment at hand doesn't systematically favor any condition over another. However, I'm not entirely sure as to how to answer this question:

Randomization, as a strategy in experimental design, would be unsuccessful if:
(A) extraneous factors varied in a systematic way.
(B) blocks could not be formed.
(C) there were an unequal "n" in the experimental groups.
(D) aspects of the experimental condition other than the values of the explanatory variable systematically favors a treatment.
(E) aspects of the experimental condition other than the values of the response variable systematically favors a treatment.


I've thought about this and think it's safe to eliminate (A) since randomization should counteract those extraneous factors. I was actually leaning towards (B), but the other answer choices seem plausible as well. I would greatly appreciate any further advice/observations to steer me in the right direction on this one. Thanks!
 
Last edited: