SAT Reading & Writing · Text Structure and Purpose
Young sunflower heads follow the sun's path from east to west during the day, then reorient back toward the east overnight, a movement…
Young sunflower heads follow the sun's path from east to west during the day, then reorient back toward the east overnight, a movement driven by asymmetric stem growth controlled by the plant's internal circadian clock instead of by any direct, moment-to-moment response to sunlight. Once sunflowers mature and begin to bloom, however, most stop this daily tracking behavior and remain fixed facing east.
Which choice best describes the function of the final sentence in the text?
Which choice best describes the function of the final sentence in the text?
Answer and explanation
Answer: B: It qualifies the earlier description by specifying that the tracking behavior is limited to a particular stage of the plant's development.
The final sentence doesn't dispute the young-plant tracking behavior described earlier; it adds a developmental boundary, specifying that the behavior changes once the plant matures. B captures that qualifying, boundary-setting function precisely. A misreads the sentence as a contradiction of the earlier claim, which it doesn't dispute. C overstates the finding into a claim about all growth or movement, when the passage specifically addresses sun-tracking. D misdescribes a directly related developmental detail as an unrelated topic shift.
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