Overuse of antibiotics often leads to a reduction in the effectiveness of the drugs; this theory has recently been bolstered by observations that people who regularly take antibiotics have fewer disease-fighting organisms in their bodies than do people who rarely take antibiotics.

A Overuse of antibiotics often leads to a reduction in the effectiveness of the drugs; this theory has recently been bolstered by observations that people who regularly take antibiotics have fewer disease-fighting organisms in their bodies than do people who rarely take antibiotics.

B If overused, one theory in regard to antibiotics becoming reduced in their effectiveness has recently been bolstered by observations that people who regularly take antibiotics have fewer disease-fighting organisms in their bodies than do people who rarely take antibiotics.

C If overused, one theory regarding antibiotics becoming reduced in their effectiveness has recently been bolstered by observations that people who regularly take antibiotics have fewer disease-fighting organisms in their bodies than those who rarely take antibiotics.

D The observation that people who regularly take antibiotics have fewer disease-fighting organisms in their bodies than do people who rarely take antibiotics has recently given support to one theory in regard to this phenomenon, if overused, antibiotics become reduced in their effectiveness.

E The observation of people who regularly take antibiotics having fewer disease-fighting organisms in their bodies than do people who rarely take antibiotics has recently bolstered one theory about why antibiotics become reduced in their effectiveness.

OA is A
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