Which of the following most logically completes the passage?

Leptin, a protein occurring naturally in the blood, appears to regulate how much fat the body carries by speeding up the metabolism and decreasing the appetite when the body has too much fat. Mice that do not naturally produce leptin have more fat than other mice, but lose fat rapidly when they are given leptin injections. Unfortunately, however, leptin cannot be used as a dietary supplement to control fat, since __________.

Answer Choices

Correct answer marked below

the digestive system breaks down proteins before they can enter the bloodstream

Correct

there are pharmaceuticals already available that can contribute to weight loss by speeding up the metabolism

people with unusually low levels of leptin in their blood tend to have a high percentage of body fat

the mice that do not naturally produce leptin were from a specially bred strain of mice

mice whose bodies did produce leptin also lost some of their body fat when given leptin injections

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Comments

MirzebeyevaJul 13

thanks, this one was quick. the passage basically hands you the answer if you know what 'dietary supplement' implies about digestion.

SahilJul 23

yeah i think the keyword is 'supplement' — it has to survive the stomach, and proteins generally don't.

HarshMay 21

wait why is D wrong? the mice being specially bred kind of seems like it could weaken the argument too

AnshumanJul 22

Easy one but B tripped me up for a second — other weight loss drugs existing doesn't mean leptin can't also be used, so it doesn't complete the 'since' clause.

HarmanJul 31

right, B is irrelevant to whether leptin itself could work. tempting because it sounds sciencey though

AhadSep 22

confused why C is even there, low leptin and high body fat doesn't explain why it can't be a supplement

What this question tests

What it tests

Whether you can complete the last sentence of an argument in a way that is logically consistent with it.

Common trap

Choosing an option that sounds plausible but contradicts the argument or introduces new information.