人体代谢所产生的能量等于消耗于体外做功的能量和在体内直接、间接转化为热的能量的总和。
参考答案：对
以质量守恒定理解释：纸在空气中燃烧后化为灰烬，灰烬的质量比纸的质量减小．
As nobody here knows what is wrong with the machine，we must send for an engineer to______
the problem.[ ]
A．handle
B．raise
C．face
D．present
