HgSO4 adds an alcohol to an alkene or alkyne in a markovnikov fashion. If it adds to an alkyne (triple bond) than you still have a double bond present after the addition of hydroxide. The trick in this problem is that the intermediate does a tautomeric ****, which puts the double bond, that was previously on the alkene, and makes a ketone. NaBH4 can reduce ketones to secondary alcohols. Hope that helps.
