Which mineral/metal witnessed the minimum growth rate in production from 2006 to 2010?

The growth rate of Aluminum from 2006-2010 = $$\dfrac{99-75}{75} \approx 33.33\%$$

The growth rate of Coal from 2006-2010 = $$\dfrac{116-88}{88} \approx 28.8\%$$

The growth rate of Copper from 2006-2010 = $$\dfrac{97-75}{75} \approx 29.33\%$$

The growth rate of Gold from 2006-2010 = $$\dfrac{20-18}{18} \approx 11.11\%$$
Thus, Gold witnessed the minimum growth rate in production from 2006 to 2010.
Hence, option D is the correct answer.