Graduate Pharmacy Aptitude Test (GPAT) 2012 Solved Paper

Read the following statements about SN1 reactions:
[P] : They proceed with complete inversion (Walden inversion).
[Q] : They proceed with racemization plus some net inversion.
[R] : They are characterized by rearrangements.
[S] : They are characterized by the reactivity sequence, CH‌3>1∘>2∘>3∘
Choose the correct combination?