Answer: B) radon Explanation: The seven elements — helium, neon, argon, krypton, xenon, radon, and oganesson of Group 18 of the periodic table are Noble or Inert gases.   Radon is the heaviest and Helium is the lightest gases of the noble gases.

Answer: C) 2 Explanation: 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.