▲閱讀下文，回答第 46-50 題
     Oftentimes people are warned not to drink coffee in the evening because it might lead tosleeping problems at night. However, research has found that cigarettes and wine may have agreater impact on disturbing the sleeping pattern than coffee does.
     A longitudinal study published in 2019 investigated the relationship between people’s useof nicotine, alcohol, and caffeine in the evening and their night sleep. 785 African Americansparticipated in this study for over a combined period of 5,000 days. During the process of theresearch, the participants were asked to hand in a sleep diary and wear a wrist-watch-like sensorto track their sleep behavior. Unfortunately, the amount of having nicotine, alcohol, and caffeinewas not recorded.
     The research found that regardless of the participants’ age, gender, stress, and other factors,the use of nicotine within four hours before bed reduced about 43 minutes in overall sleep. Also,consuming alcohol in the evening resulted in the difficulty in falling asleep and sleepingcontinuity. Although people tend to smoke or drink wine before bed to increase sleep quality,the outcome is the opposite.Interestingly, having coffee before sleep did not necessarily influence sleep length, the timeneeded for falling asleep, and overnight sleep. The scientists explained that because everyone’ssensitivity and tolerance of caffeine were different, people may have different reactions to thesame amount of coffee intake.
     In conclusion, from the study, nicotine and alcohol are confirmed not to be the best choicesif anything important is scheduled in the early morning next day. As for caffeine, it depends onindividuals. Future studies should examine the level of influences caused by the amount ofsmoking or drinking alcohol before bedtime.
46. What is the main idea of the passage?
(A) Smoking and drinking alcohol do cause sleeping difficulties.
(B) People must not smoke, drink wine or coffee before they sleep.
(C) Drinking coffee before bed definitely causes sleeping problems.
(D) The use of nicotine, alcohol, and caffeine should be recorded daily.