When grace reached her 70s, she began having difficulty falling asleep, staying asleep, and sleeping deeply. during the day, grace worried about having sleep trouble. one thing grace could do to foster restful sleep is

The correct answer should be use the bedroom only for sleep.
If Grace creates the connection between her bedroom and sleep, she will condition herself to start feeling sleepy every time she enters the bedroom. If she only uses the bedroom for sleep, and not for resting, or reading, then she is likely to have a good night's sleep and solve this problem.