This is a Must Be True question. Note that the question stem contains the phrase "properly inferred," which is common of the Must Be True question type.
The passage tells us that lab rats used for research regarding improving human health are normally kept in small cages, which is an abnormal and unhealthy environment for them. The reliability of research that uses animals in abnormal environments is diminished.
What can we conclude from this? We know that research reliability is diminished when animals are kept in abnormal environments, and we know that the lab rats used for research regarding improving human health are normally kept in abnormal environments, so we can infer that the reliability of this research is diminished. Answer choice (C) rephrases this concept as "research using laboratory mice that is aimed at improving human health is compromised by the conditions under which the mice are kept." Therefore, (C) is correct.
(A) is incorrect because the passage does not indicate anything about the future. (B) is incorrect because we know that lab rats kept in these poor conditions diminish research reliability, but we don't necessarily know that this is the only issue concerning them or the larger issue of their appropriate use in the research. (D) is incorrect because, as in (A), we do not know anything about the future. (E) is incorrect because we are given no information on lab rats that are used for other purposes.
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