Which company has the highest average production over the three years?

Answer: Option C

$$\begin{array}{rl}& \text{A}=\frac{20+30+20}{3}\\ & =\frac{70}{3}\\ & =23.33\\ & \\ & \text{B}=\frac{40+30+50}{3}\\ & =\frac{120}{3}\\ & =40\\ & \\ & \text{C}=\frac{20+20+40}{3}\\ & =\frac{80}{3}\\ & =26.66\\ & \\ & \text{D}=\frac{60+30+40}{3}\\ & =\frac{130}{3}\\ & =43.33\end{array}$$
So company D has the highest production.