PSAT Reading & Writing Question of the Day
Test your knowledge with a hand-picked multiple-choice question.
Most sleep research has focused on the effects of screen time, but light exposure itself may matter just as much. In a small experiment, participants spent two weeks following their usual routines and two weeks limiting bright light after sunset; activity trackers measured sleep onset and duration. During the light-limited period, participants fell asleep sooner and stayed asleep longer, even though they used their phones just as often. The researchers also noted improved alertness the following morning. These results indicate that moderating evening brightness, not merely reducing device use, can improve sleep quality. The team plans a larger trial to test whether simple changes, such as dimming household bulbs or using warmer settings, yield similar benefits across different age groups.
Which choice best describes the function of the underlined sentence in the overall structure of the text?