Official Explanation:
The original sentence incorrectly uses a past tense verb form: “maintained.” This is inconsistent with the present tense verbs “exercise” and "are." The present tense is appropriate here because the study in question asserts that the women who perform certain behaviors on an ongoing basis (present tense) are (present tense) at a low risk of death. Additionally, the phrase “physical exertion that is moderate to vigorous in nature” is unnecessarily wordy. The more concise “moderate to vigorous physical exertion” is preferred.
(A) This choice is incorrect as it repeats the original sentence.
(B) CORRECT. The present tense verbs “maintain” and “are” are consistent with the present tense verb “exercise.” Also, the phrase “moderate to vigorous physical exertion” is clear and concise.
(C) This choice incorrectly uses a future tense verb form: “will be.” This is inconsistent with the present tense verbs “exercise” and “maintain.”
(D) This choice incorrectly uses past tense verb forms: “maintained” and “were.” These are inconsistent with the present tense verb “exercise.”
(E) The phrase “physical exertion that is moderate to vigorous in nature” is unnecessarily wordy. The more concise “moderate to vigorous physical exertion” is preferred.