详细地说明供应和需求作用是如何确定价格。
Elaborate how price is determined by the actions of supply and demand.
公共图书馆除了继续发挥重要的教育作用外，还提供文化和娱乐，并努力满足社区不断变化的需求。
In addition to their continuing and important educational role, public libraries provide culture and recreation, and they are trying to fill many changing community needs.
由于员工需求不同，对一个人起强化作用的措施可能对另一个人不起作用。
Since employees have different needs, what acts as a reinforcement for one may not for another.
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