过两点M_1(3,-2,1)和M_2(-1,0,2)的直线方程为（）A. (x+1)/(3)=(y)/(-2)=(z-2)/(1).B. (x-3)/(-4)=(y+2)/(2)=(z-1)/(1).C. (x-3)/(-1)=(y+2)/(0)=(z-1)/(2).D. (x-3)/(2)=(y+2)/(-2)=(z-1)/(3).

A. $\frac{x+1}{3}=\frac{y}{-2}=\frac{z-2}{1}$.

B. $\frac{x-3}{-4}=\frac{y+2}{2}=\frac{z-1}{1}$.

C. $\frac{x-3}{-1}=\frac{y+2}{0}=\frac{z-1}{2}$.

D. $\frac{x-3}{2}=\frac{y+2}{-2}=\frac{z-1}{3}$.