[单项选择]

联合国关于发展的观念经历了一个演变过程：20世纪五六十年代把发展归结为经济增长；20世纪70年代把发展看作是经济增长、经济结构优化和社会变革；从20世纪八九十年代开始，把发展理解为注重资源节约、环境保护的可持续发展和以人为中心的综合发展。联合国关于发展的观念演变进一步证实了（）
①认识的不断完善决定着实践的不断深化
②认识受认识对象本质和属性暴露程度的制约
③认识的发展具有与认识主题无关的客观规律性
④认识的发展是一个不断继承和超越已有认识成果的过程

A. ①②
B. ①③
C. ②④
D. ③④

Judging from recent surveys, most experts in sleep behavior agree that there is virtually an epidemic of sleepiness in the nation. "I can’t think of a single study that hasn’t found Americans getting less sleep than they ought to." says Dr. David.
The beginning of our sleep deficit crisis can be (1) to the invention of the light bulb a century ago. From diary entries and other personal (2) from the 18th and 19th centuries, sleep scientists have reached the conclusion that the average person used to sleep about 9.5 hours a night. By the 1950s and 1960s, that sleep schedule had been reduced (3) , to between 7.5 and 8 hours, and most people had to wake to an alarm clock. "People cheat on their sleep, and they don’t even (4) they’re doing it," says Dr. David. "They think they’re okay because they can get by on 6.5 hours, when they really need 7.5, 8 or even more to feel ideally (5) <
A. consequences
B. complexity
C. ingenious
D. dramatically
E. suffers
F. tracked
G. realize
H. expensive
I. slightly
J. traced
K. detaches
L. vigorous
M. inspiration
N. accounts