Answer:
The correct heading for a long essay about various activities to do at the beach is 'Parasailing, Hang-gliding, Snorkeling, and more!'
Explanation:
This is the perfect heading for an essay regarding activities to do at the beach since it names several activities that are typically done there.
<em>'What to wear this summer'</em> is not a possible option since this heading is possibly aimed at the summer 'trends/craze', that is to say, what people want to wear to fit in with the rest.
'<em>Writing a Postcard</em>' is not suitable because this is not normally done at the beach, it is rather done at home or the apartment. Plus, it only describes one acitvity, not various.
Finally, <em>'Choosing a Sunscreen</em>' is not possible either because it also describes one single activity and one that is usually done <em>at a shop</em> or <em>before going to the beach.</em>
