Right answer: se despiertan
The second sentence is written with the 3rd person in plural ellos (they), which are mis padres (my parents), hence the correct conjugation from the given options of the verb despertar (to wake up) with this subject is despiertan (they wake up).
In addition, despertar is a pronominal verb, this means it needs to be conjugated with a reflexive pronoun, which agrees in person and number with the subject, to express emphasis.
In this case the reflexive pronoun according to the 3rd person in plural is se.
In this way it is indicated that the action the subject Mis padres performs falls on it at the same time indicating that the action directly affects the subject
Therefore the correc option is d:
se despiertan
And the whole sentence is:
Mis padres se despiertan a las seis de la mañana.
My parents wake up at six in the morning.