The question is asking which reagents can be used to carry out this reaction. I get the L (PCC) is used to turn the primary alcohol into an aldehyde. However, I believe that is not the only reagent needed as the tertiary alcohol -OH must become -O- for the reaction to be SN2. A strong nucleophile is needed to carry out the formation of the SN2 reaction that forms the ring as the aldehyde is only primary (thus SN2 needed). I think that J, the tertbutoxide or S (NaOH) will deprotonate the OH group on the tertiary alcohol for the reaction to proceed.
Why is only L needed and not L and J (or S)?