We are given 4 forms of the verb "enseñar" (to teach) in the present tense (presente de indicativo).
Conjugation of verbs ending in -ar.
To find the conjugation of most verbs ending in -ar, replace "ar" with the following endings: o, as, a, amos, áis, an.
Since "enseñar" is a regular verb, its conjugation is as follows:
Yo enseño
Tú enseñas
Él / ella / usted enseña
Nosotros /nosotras enseñamos
Vosotros / vosotras enseñáis
Ellos / ellas / ustedes enseñan
Now, let's pay attention to the subject of the sentence. "Ellas" refers to a group of women and translates to "they," the third-person plural.
Therefore, the correct option is C:
Ellas enseñan inglés.
Translation: They teach English.