A：速度v与路程s成正比
B：路程s与速度v成正比
C：当速度一定时，路程s与时间t成正比
D：速度v与时间t成反比
— Did you hear the news about the fire in our building?
— Yes. It took the firemen two hours to_______ the fire.
生态系统一般都包括（ ）
