|A) 4||B) 3|
|C) 2||D) 1|
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.