Randomization, as a Strategy in Experimental Design, Would Be Unsuccessful

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.