PT 50 S4 Q23

Many scientific studies have suggested that taking melatonin tablets can ... ...

Which one of the following, if true, most strengthens the argument?
(A) A weaker correlation between taking melatonin and the inducement of sleep was found in the studies that included people with insomnia than in the studies that did not.
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Practice Set: "Stronger" Questions, Set 3 - Difficult/Uncommon Mix (25Q)