Why is sodium stored in kerosene?

Explanation:

The correct answer is option B i.e. sodium (Na) is highly reactive and burns in air.

Sodium (Na) being an alkali metal, is highly reactive and occupies amongst the top spots in the metal reactivity series. Na reacts vigorously with  oxygen as well as moisture present in atmosphere, leading to accidental fires.So, in order to prevent it from coming in contact with surrounding atmosphere and it's constituents, it is stored in kerosene which renders it non-reactive ,thus preventing it's vigorous reactions as well as accidental fires.

Option A which states that Na sublimates if kept in open is incorrect as Na is quite heat stable and doesn't sublimate, while option C is incorrect as rusting is a phenomenon of oxidation seen in Fe and it's compounds.

Final Answer:

Hence, the correct answer is option B i.e. Na is stored in kerosene as it is highly reactive and burns in air.