Official Explanation given my
Manhattan Prep :
A properly inferred conclusion must be arrived at by necessary logical deductions, without any additional assumptions. Thus, the correct answer to this problem must be a necessary logical consequence of the statements in the passage.
(A) Correct. The passage states that patients taking the drug will experience losses of both body fat and lean mass, but does not state the relative amounts in which the two components of weight will be lost. In order to ascertain whether the subjects’ body fat percentage will go down, we need to know two ratios: the patients’ original ratio of fat to lean mass, and the ratio of fat lost to lean mass lost. Without definite figures for either of these ratios, the patients could lose fat and lean mass at relative rates that would either increase or decrease their percentages of body fat.
(B) The passage states that all patients taking the drug experience losses of both body fat and lean mass. Per the passage, these are the only two components of the subjects’ body weight, so, if the subjects experience losses in both components, then they must lose weight overall.
(C) The loss of lean mass does not imply that the drug cannot contain a chemical that targets the body’s fat cells exclusively. For instance, the drug could contain such a chemical along with other chemicals (perhaps necessary for other reasons, such as proper digestion or transport) that cause the losses in lean mass.
(D) Nothing in the passage is pertinent to the issue of preventing the loss of lean mass from the drug, so no such conclusion is justified.
(E) No information about the mechanism by which the drug catalyzes fat and lean-mass losses is presented in the passage, so no such conclusion is justified.
The correct answer is A.