Convert benzene to isopropylbenzene
You are right, both abstracting $\ce{Cl-}$ from the alkyl chloride with Lewis acid as well as dehydration of isopropanol with $\ce{H2SO4}$ are suitable ways to generate the 2-propyl carbocation, your electrophile in this reaction. Option (c) will not work because $\ce{AlCl3}$ reacts with alcohols to form aluminium alkoxides.

Source: Master Organic Chemisry