20、任意的化学反应aA+bB=cC+dD，则它的速率表达式正确的是：A. (dc_(A))/(dt)=(dc_(B))/(dt)B. -(dc_(D))/(dt)=(dc_(A))/(dt)C. (1)/(c)(dc_(C))/(dt)=-(1)/(b)(dc_(B))/(dt)D. -(1)/(a)(dc_(A))/(dt)=(1)/(b)(dc_(B))/(dt)

A. $\frac{dc_{A}}{dt}=\frac{dc_{B}}{dt}$

B. $-\frac{dc_{D}}{dt}=\frac{dc_{A}}{dt}$

C. $\frac{1}{c}\frac{dc_{C}}{dt}=-\frac{1}{b}\frac{dc_{B}}{dt}$

D. $-\frac{1}{a}\frac{dc_{A}}{dt}=\frac{1}{b}\frac{dc_{B}}{dt}$