Answer: a. 2K + I2 => 2 KI
Explanation: Potassium or K is in group 1 so its oxidation is 1+ while Iodine is in group 7 so its oxidation is -1. Iodine is expressed as I2 when written individually. So the reaction is K reacts with I2 to produce KI. Then balance the equation by adding 2 to K and 2 to KI to balance the equation.