Answer: Option (c) is the correct answer.
Step-by-step explanation:
Elements of group 1 are lithium, sodium, potassium, rubidium, cesium and francium. Each element of this group contains 1 valence electron and in order to acquire stability they readily lose its one valence electron.
On the other hand, elements of group 2 contain two valence electrons and hence, they need to lose two valence electrons. Whereas transition metals lose one or more than one electrons and thus they show variable oxidation states.
Reactivity is the ability of a substance to lose or gain an electrons easily.
Therefore, we can conclude that alkali metal is the group of elements which contains the most reactive metals.