阅读下面这则材料，用一句话概括其主要内容。

　　11月17-18日，第六届全国中小学党建工作研讨会在我市励才实验学校召开，来自北京、上海、天津、湖北、广东、内蒙等二十多个省市自治区的代表以及我市各中小学校长书记200多人参加研讨。会议期间，为彰显学校的办学特色，展现师生的精神风貌，励才实验学校举行了千人武术操表演、师生优秀书法作品展等活动，为与会代表献上了一份精神大餐。

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The process of gaining or losing weight can be explained by comparing your body to your car. Both run (51) fuel, food for your body and gasoline for your car. Both (52) that fuel, first into heat, then energy, some of (53) is used to do work, and some emitted as waste. And (54) your car uses more energy when the engine is racing than when it is idling, (55) does your body use more energy when you are working hard than (56) you are resting.

For the purpose of this comparison, (57) , there is one significant difference between them. Your car cannot store fuel by turning it into (58) else; all gasoline not (59) remains as gasoline. But your body stores (60) energy as fat. When the gas tank is completely empty, the car won’t run; but your body can burn fat to provide more energy.

56().

A.that 

B.since 

C.when 

D.where