Questions

Here the most stable carbocation is the option (2).

Carbocations are always hungry for electrons. The stability of carbocations increases from primary to secondary to tertiary. Here, option (c) shows the most stable carbocation because it can easily withdraw electrons from two other carbon atoms and the more electronegative oxygen atom.

Carbocation stability depends on hyperconjugation. The tertiary carbocation is stabilized by electron releasing inductive effect.

The given letter equation puzzle means that 

7 W of the W = 7 Wonders of the World.

Nitrous acid act as an oxidising agent because it oxidises potassium iodide to iodine. It is also a reducing agent because it decolourises acidified potassium permanganate solution.

Nitric acid acts only as an oxidising agent

Ammonia acts only as a reducing agent

Nitrogen peroxide acts only as an oxidising agent.

This is the reason why we see the same side of  the moon always