Salvavidas: señor, por favor. sr. garcía: está bien. nade cerca de la costa. usa bloqueador solar. nada con otras personas. usa gafas de sol.

Nade cerca de la costa.

Explanation:

IN this sentence the two speakers are the lifeguard and Mister García, from the information in the sentence we can see that the lifeguard is asking MR garcía to do something, to what he agrees:

Lifeguard: Mr. please

Mr. Gracia: Al right

And the options are:

Swim closer to the shore, Put on some sunscreen, Swim with other people, USe sunglasses.

As you know the verbs in spanish are conjugated depending on the person performing the actions, so this should be conjugated in the third person and only the first one "Nade cerca de la costa" is conjugated like that, so that would be the correct answer.