Question

stem changing verbs e - ie, sa
ellos a jugar tenis.
emplezan empiezan empezar empezamos

Explanation:

In Spanish, the subject "ellos" (they) requires the third - person plural form of the verb. The verb "empezar" (to start) is a stem - changing verb (E - IE in the present tense for certain forms). For "ellos", the correct form is "empiezan".

Answer:

empiezan