Question

Sodium, potassium and lithium are stored under oil.(Give reasons)

Answer 1

Because these are highly reactive metals and could catch fire by reacting with oxygen in the presence of air.

...........that's why they are stored under oil to prevent their contact with oxygen.

or

Metals like sodium, potassium and lithium are highly reactive and react with air at room temperature. So, in order to break their contact with air, they are stored in liquid hydrocarbons like kerosene oil, as kerosene is lighter than any of these metals.

Hope this will help you.... ✌