PT 64 S1 Q4

Physician: In an experiment, 50 patients with chronicback pain were divided ... ...

Which one of the following, if true, constitutes the logically strongest counter to the physician’s argument?
(A) A patient’s merely knowing that a treatment has been applied can lead to improvement in his or her condition.
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Oct 2011 LSAT (PT 64): Logical Reasoning A