—Americans spend more on health care than most other people .

— You’re right . But a new study shows that life      in the United States is falling .

A．development

B．position

C．experience

D．expectancy

含蛋白质丰富的食物发生腐败变质最敏感和最可靠的鉴定指标为（）。

A.感官指标

B.微生物指标

C.化学指标

D.物理指标

E.实验室指标