We can use the reactivity series of metals to solve this.
The reactivity series of metals are (in descending order) :
Potassium, sodium, Lithium, calcium, Magnesium, aluminum, zinc, iron, tin, lead, copper, mercury, silver, platinum, gold.
Since Potassium is the most reactive, the reaction with water should produce extremely violent gas.
Sodium is the next most reactive, so it should produce violent gas.
And Lithium is the least reactive out of the 3 metals, so it should be strong gas formation.
In addition, the gas produced should be hydrogen, since the reaction of metals should water should produce "metal name" hydroxide + hydrogen.
