Final answer:
The correct verb is 'oyeron'
Step-by-step explanation:
In the given sentence, the correct verb to fill the blank is 'oyeron'.
When translating the sentence to English, it reads: 'The students did not hear the instructions.'
Here, 'oyeron' is the correct past tense form of the verb 'oír' (to hear) for the subject 'estudiantes' (students).
Learn more about Verb usage in Spanish