Which phrase correctly completes this conversation between two friends? ana: gloria, ¿qué precaución debo tomar si quiero nadar en el mar? gloria: es necesario cerca de la costa. que nada que nades que nado

The correct answer is option b. que nades ("that you swim").

Explanation:

In Spanish, when giving orders, advices or expressing some sort of imperative, it is used the present subjunctive, in which the rule goes: the word "que" ("that") + "verb in subjunctive". To get to the subjunctive conjugation, you have to refer to the verb in the infinite form (verb with termination -ar changes to -e; and verbs with termination -er/-ir changes to -a).

The verb in the sentence is "nadAR" which has a termination -ar, so the termination changes into -e in subjunctive. And as Gloria is referring directly to Ana, that is, to the second person singular (you), then you have to add an "s" at the end of the verb, so the correct conjugation must be "nades". Now, adding the word "que", the correct answer goes: "que + nade+s". And for that reason, the correct answer is option b. que nades.

The other two options are following the rule of subjunctive by using the word "que" before the verb, but not all verbs are conjugated correctly. In Option a. "que nada"  the verb is conjugated in the present subjunctive but for the third person singular, and therefore incorrect. And in option c. "que nado" the verb is conjugated in the present indicative for the first person singular, also incorrect.