Answer

A-R; B-Q,C-S ; D-P

Explanation

2-Methyl cyclohexanol `overset("conc."H_2SO_4)to` (R) 1-Methylcyclohexene
cyclopentylmethanol `overset("Conc."H_2SO_4)to`(Q) Cyclohexene
1-methyl – 1-cyclopen tan ol `overset("Conc."H_2SO_4)to` (S) 1-Methlcyclopentene
2,2 Dimethylcyclohexanol - `overset(Conc. H_2SO_4)to` (P) 1,2-Dimethylcyclohexene