单选题Directions:Read the following text. Choose the best word
(s) for each numbered blank and mark A, B, C or D.
Ancient Greek philosopher Aristotle viewed laughter as "a bodily exercise
precious to health. " But {{U}} {{U}} 1 {{/U}} {{/U}}some claims
to the contrary, laughing probably has little influence on physical fitness
Laughter does {{U}} {{U}} 2 {{/U}} {{/U}}short-term changes in
the function of the heart and its blood vessels, {{U}} {{U}} 3
{{/U}} {{/U}}heart rate and oxygen consumption But because hard laughter is
difficult to {{U}} {{U}} 4 {{/U}} {{/U}}, a good laugh is
unlikely to have {{U}} {{U}} 5 {{/U}} {{/U}}benefits the way,
say, walking or jogging does. {{U}} {{U}} 6
{{/U}} {{/U}}, instead of straining muscles to build them, as exercise does,
laughter apparently accomplishes the {{U}} {{U}} 7 {{/U}}
{{/U}}, studies dating back to the 1930's indicate that laughter {{U}}
{{U}} 8 {{/U}} {{/U}}muscles, decreasing muscle tone for up to 45
minutes after the laugh dies down. Such bodily reaction might
conceivably help {{U}} {{U}} 9 {{/U}} {{/U}}the effects of
psychological stress. Anyway, the act of laughing probably does produce other
types of {{U}} {{U}} 10 {{/U}} {{/U}}feedback, that improve an
individual's emotional state. {{U}} {{U}} 11 {{/U}} {{/U}}one
classical theory of emotion, our feelings are partially rooted {{U}}
{{U}} 12 {{/U}} {{/U}}physical reactions. It was argued at the end
of the 19th century that humans do not cry {{U}} {{U}} 13
{{/U}} {{/U}}they are sad but they become sad when the tears begin to
flow. Although sadness also {{U}} {{U}} 14
{{/U}} {{/U}}tears, evidence suggests that emotions can flow {{U}}
{{U}} 15 {{/U}} {{/U}}muscular responses. In an experiment published
in 1988, social psychologist Fritz Strack of the University of wiirzburg in
Germany asked volunteers to {{U}} {{U}} 16 {{/U}} {{/U}}a pen
either with their teeth-thereby creating an artificial smile-or with their lips,
which would produce a (n) {{U}} {{U}} 17 {{/U}}
{{/U}}expression. Those forced to exercise their smiling muscles {{U}}
{{U}} 18 {{/U}} {{/U}}more exuberantly to funny cartons than did
those whose mouths were contracted in a frown, {{U}} {{U}} 19
{{/U}} {{/U}}that expressions may influence emotions rather than just the
other way around {{U}} {{U}} 20 {{/U}} {{/U}}, the physical act
of laughter could improve mood.