48. What does the word, impairment, mean? (A) Improvement. (B) Damage. (C) Repair. (D) Function.

49. According to the passage, which one of the following statements is the benefit of having enough sleep? (A) It makes the hippocampus grow. (B) The brain works to clear the shortterm memories to increase storage. (C) The brain works to associate some shortterm memories to other areas, and those memories become longlasting. (D) It prevents mild cognitive impairment.