The fourth proportional to 0.12, 0.21 and 8 is-

Answer: Option B

Let the fourth proportional to 0.12, 0.21 and 8 be x
$$\begin{array}{rl}& \text{Then,}\\ & =\text{0}\text{.12}:\text{0}\text{.21}::\text{8}:x\\ & \Rightarrow \text{0}\text{.12}x=0.21\times 8\\ & \Rightarrow x=\frac{0.21\times 8}{0.12}\\ & =\frac{21\times 8}{12}\\ & =14.\end{array}$$