The value of tan 4°.tan 43°.tan 47°.tan 86° is?

Answer: Option C

$$\begin{array}{rl}& \text{tan }{\text{4}}^{\circ }\text{.tan 4}{\text{3}}^{\circ }\text{.tan 4}{\text{7}}^{\circ }\text{.tan 8}{\text{6}}^{\circ }\\ & \text{Here, }\\ & \text{tan 8}{\text{6}}^{\circ }=\text{tan}\left(\text{ 9}{\text{0}}^{\circ }-4^{\circ }\right)=\text{cot }{\text{4}}^{\circ }\\ & \text{tan 4}{\text{7}}^{\circ }=\text{tan}\left(\text{ 9}{\text{0}}^{\circ }-{43}^{\circ }\right)=\text{cot 4}{\text{3}}^{\circ }\\ & \text{tan }{\text{4}}^{\circ }\text{.cot }{\text{4}}^{\circ }\text{.tan 4}{\text{3}}^{\circ }\text{.cot 4}{\text{3}}^{\circ }=1\end{array}$$