試題詳解

48. According to the passage, which of the following could be the weakness of this research?
(A) The number of people participating in this study was not enough.
(B) The amount of nicotine, alcohol, and caffeine consumed was not recorded.
(C) The number of factors that could affect people’s sleep at night was not controlled.
(D) The amount of time before bed the participants should consume nicotine was not shown.