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参考答案：
某农村地区，农民家庭电视拥有率为20%，家家户户都可以收听到有线广播内容有农村环境卫生、疾病预防等健康信息。如果主要选择电视为健康传播媒介即违背了媒介选择的（）
A.保证效果原则
B.针对性原则
C.速度快原则
D.可及性原则
E.经济性原则
A decorator bought a bolt of defective cloth that he judged to be
usable, in which ease the cost would be $0.80 per usable yard. If it was later found that only
of the bolt could be used, what was the actual cost per usable yard
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usable, in which ease the cost would be $0.80 per usable yard. If it was later found that only 
of the bolt could be used, what was the actual cost per usable yard