We know that the addition and elimination reactions are opposite of each other.Hence, for solving the above questions our approach should be to first dehydrate a suitable alcohol to give either a single alkene or a mixture of an alkene, if we obtain a mixture of alkene then we would have to detect which of the alkene will give us the desired alcohol. Wherever required the acid-catalyzed addition of water to alkenes will follow Markovnikov’s rule.

Now, upon addition of H₂O to pent-1-ene we obtain the desired product.

But the addition of H₂O to pent-2-ene gives us a mixture of two alcohols out of which one is desired and the other one undesired.

Hence, the alkene to be chosen to arrive at the desired alcohol as the product should be pent-1-ene as it gives only a single product which is the desired alcohol.