The common difference of the A.P. 1/3, 1 - 3b3, 1 - 6b3, . . . . . . is

Answer: Option C

$$\begin{array}{rl}& \text{A}\text{.P}\text{.is}\frac{1}{3},\frac{1-3b}{3},\frac{1-6b}{3},......\\ & \Rightarrow \frac{1}{3},\frac{1}{3}-\frac{3b}{3},\frac{1}{3}-\frac{6b}{3},......\\ & \Rightarrow \frac{1}{3},\frac{1}{3}-b,\frac{1}{3}-2b,.......\\ & \therefore d=\left(\frac{1}{3}-b\right)-\frac{1}{3}\\ & =\frac{1}{3}-b-\frac{1}{3}\\ & =-b\end{array}$$