1. The most stable pair is Ph3C(CH3)3C, as tertiary carbocations are more stable than secondary carbocations. 2. The reaction of (-)-1-chloro-1-phenyl ethane in toluene forms a carbocation due to the presence of SbCl5. 3. The order of stability of the carbocations is III > II > I, as tertiary carbocations are more stable than secondary which are more stable than primary carbocations.