精选优质文档-倾情为你奉上专业四级(TEM-4 2004)The normal human daily cycle of activity is of some 7-8 hours sleep alternation with some 16-17 hours wakefulness and that the sleep normally coincides (31) the hours of darkness . Our present (32) is with how easily and to what extent this (33) can be modified.The question is no mere academic one. The ease (34) people can change from working in the day to working at night is a (35) of growing importance in industry where automat
