The "Sensitivity" of an Experiment Refers to Its Ability to Detect

The "sensitivity" of an experiment refers to its ability to detect any differences in performance, however small, between the two groups. In one technique to improve sensitivity the experimenter uses matching of participants across groups, assuring that

A) generalization to the population can be made.
B) groups of participants are equated on those selected extraneous matching variables.
C) the performance of a participant in one group is statistically equated with the performance of that participant's partner in another group.
D) groups are equated on all possible variables.