题目内容
自然循环供暖系统靠（ ）来排气。
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机械循环供暖系统是靠（ ）作为循环动力的。
机械循环供暖系统供水干管的坡向和坡度分别为（ ）。
Listen to the five short conversations and tell whether the statements are true or false. Write T for true and F for false. Mr. Li, the sales representative, isconducting a market survey.
Linda does not know much about theproducts and their prices.
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