Step 1: Propene (\( C_3H_6 \)) reacts with HBr in the presence of ROOR to form 1-bromopropane via anti-Markovnikov addition.
Step 2: 1-bromopropane undergoes Friedel-Crafts alkylation with benzene and AlCl3, forming n-propylbenzene.
Thus, the correct sequence is HBr/ROOR.