Final answer:
The correct phrase to complete the sentence is 'hicieron'.
Step-by-step explanation:
The correct phrase to complete the sentence is D. hicieron. The sentence is talking about the past, so the verb should be in the preterite tense. 'Hicieron' is the correct conjugation for 'ellos' (they) in the preterite tense of the verb 'hacer' (to do).
Learn more about Conjugation of verbs in Spanish