11. ¿Cuál de los siguientes metales se incendió en la reacción con el aire? A. magnesio B. manganeso C. potasio D. calcio

Answer. Explanation: Sodium and potassium both are extremely reactive and react with air as well as water vigorously. The reactions are highly exothermic and hence, the hydrogen gas evolved as byproduct catches fire.
Joyous Jaguar