OFFICIAL EXPLANATION


Generalizable, universal.

The colon in this sentence introduces an illustration of how or why the medical study is deficient. The study "assumes" one thing about the results, "however" something else is actually true. The blank, then, must contrast with "experimental participants were exclusively men between the ages of 30 and 60 with no significant co-morbidities." It helps to know that "comorbidities" are multiple diseases present simultaneously in a patient, but if you didn't, the sentence provides enough other clues to answer correctly. The "glaring deficiency" is that the "experimental participants" included no females, no un-der-30- or over-60-year-olds, and no people with "significant co-morbidities." In other words, the study was limited to a pretty specific group, so the contrasting blank should be something like "not limited." Results that are "generalizable" can be broadly applied; "universal" results are applicable to all cases. These synonyms correctly allude to the study flaws that follow "however." The adjective "positive" can mean a variety of things, including good, affirmative, optimistic, useful, or definite. When describing "results," none of those meanings addresses the study flaws listed. A similar choice is "promising," or showing signs of future success. While it would be wrong to assume that "results are promising" when the "study contains a glaring deficiency," such an assumption is not itself an example of the deficiency. “Singular” and “exceptional” both mean remarkable or unusual—almost the opposite of “universal.”