单选题
Crying is hardly an activity encouraged by society. Tears, be they of sorrow, anger, or joy, typically make Americans feel uncomfortable and 28 . The shedder of tears is likely to apologize, even when a devastating (毁灭性的) tragedy was the provocation. The observer of tears is likely to do everything possible to put an end to the 29 outpouring. But judging from recent studies of crying behavior, links between illness and crying and the chemical composition of tears, both those responses to tears are often 30 and may even be counterproductive (使达不到预期目标的). Humans are the only animals 31 known to hed emotional tears. Since evolution has given 32 to few, if any, purposeless physiological responses, it is logical to assume that crying has one or more functions that 33 survival. Although some observers have suggested that crying is a way to elicit assistance from others (as a crying baby might from its mother), the shedding of tears is hardly necessary to get help. Vocal cries would have been quite enough, more likely than tears to gain 34 . So, it appears, there must be something special about tears themselves. Indeed, the new studies suggest that emotional tears may play a direct role in alleviating stress. University of Minnesota researchers who are studying the chemical composition of tears have recently 35 two important chemicals from emotional tears. Both chemicals are found only in tears that are shed in response to emotion. Tears shed because of exposure to cut onion would contain no such 36 . Researchers at several other institutions are investigating the usefulness of tears as a means of 37 human ills and monitoring drugs. A. attention B. overwhelming C. inappropriate D. embarrassed E. diagnosing F. indispensable G. rise H. isolated I. definitely J. enhance K. aspiration L. emotional M. repelled N. substance O. increasingly