答案Part IV Reading Comprehension (Reading in depth)
47 N tend 48 L negative 49 H efficiently 50 B associated
51 A alert 52 J function/ 53 F definitely 54 O younger
55 E continuing56 G different
文章大意:本文主要讲述的是关于老年人睡眠的问题:是否老年人与年轻人相比只需要较少的睡眠时间?