<u>Answer:</u>
In Spanish, <em>sentirse</em> (to feel) is the intransitive form of the verb <em>sentir </em>(to feel).
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Sentirse</em> is also a pronominal verb, this means the verb needs to be conjugated with a reflexive pronoun, <u>which agrees in person and number with the subject, to express reflexivity and in some cases emphasis.</u>
Here the <u>Reflexive Pronouns</u> according to the subject are:
1st person singular: Yo (I) me
2nd person singular: Tú (You) te
3rd person singular: Él/Ella/eso/esa (He, She, It) se
1st person plural: Nosotros (we) nos
2nd person plural: Ustedes (You) (In latinAmerica) se / Vosotros (In Spain) os
3rd person plural: Ellos/Ellas (They) se
In this sentence the subject is<em> </em><em>ella </em>(she), which is the <u>3rd person in singular</u>, and according to the list above, the <u>reflexive pronoun </u>for <em>ella</em> is <u><em>se</em></u><em>.
</em>
Therefore, the right answer is:
<h2>Ella <u>se siente</u> enferma. </h2>