Ancient Greek philosopher Aristotle viewed laughter as "a bodily exercise precious to heal

th. " But【B1】______some claims to the contrary, laughing probably has little influence on physical fitness Laughter does【B2】______short-term changes in the function of the heart and its blood vessels,【B3】______heart rate and oxygen consumption But because hard laughter is difficult to【B4】______, a good laugh is unlikely to have【B5】______benefits the way, say, walking or jogging does.

【B6】______, instead of straining muscles to build them, as exercise does, laughter apparently accomplishes the【B7】______. Studies dating back to the 1930's indicate that laughter【B8】______muscles, decreasing muscle tone for up to 45 minutes after the laugh dies down.

Such bodily reaction might conceivably help【B9】______the effects of psychological stress. Anyway, the act of laughing probably does produce other types of【B10】______feedback that improve an individual's emotional state.【B11】______one classical theory of emotion, our feelings are partially rooted【B12】______physical reactions. It was argued at the end of the 19th century that humans do not cry【B13】______they are sad but that they become sad when the tears begin to flow.

Although sadness also【B14】______tears, evidence suggests that emotions can flow【B15】______muscular responses. In an experiment published in 1988, social psychologist Fritz Strack of the University of Würzburg in Germany asked volunteers to【B16】______a pen either with their teeththereby creating an artificial smileor with their lips, which would produce a(n)【B17】______expression. Those forced to exercise their smiling muscles【B18】______more enthusiastically to funny cartoons than did those whose mouths were contracted in a frown,【B19】______that expressions may influence emotions rather than just the other way a-round.【B20】______, the physical act of laughter could improve mood.

【B1】

A．among

B．except

C．despite

D．like