Answer: Option C
Explanation: The question is:
What happened yesterday?
Whit this, we know that the answer must be in the preterite tense or the imperfect tense.
the options are:
a) Hablo a Beto por telefono. (This is conjugated in the present tense)
b) Yo creo que es necesario hablar con nuestro gobernador. (this means "I think that we must talk with our governor" So this is not an answer to the question)
c) ayudé a mi abuelo a preparar la cena. (This option is conjugated in the preterite tense, so this is a good option)
d) Voy a Bailar Toda la Noche. (This is un future tense, so this is also discarded)
The only option that makes sense is option C.