Which phrase correctly completes this sentence? ayer, mi hermano menor la cabeza con una pelota.
a.) se golpea
b.) nos golpearon
c.) te golpeaste
d.) se golpeó

Se is the reflexive pronoun that matches the third person singular. In Spanish, we use Reflexive Pronouns with a verb to point out that a person carries out an action to or for himself or herself. So My younger brother (mi hermano menor) carries out the action to hit with the ball for himself. On the other hand, golpeó is the conjugation of the verb golpear that matches the third person singular in the preterite tense. Finally:

Ayer, mi hermano menor se golpeó la cabeza con una pelota.

read the text, then mark the beginning, the node and the outcome, and point out the characteristics of the quantum manifested in the story

the black sheep

in a distant country a black sheep existed many years ago, was shot.

a century later, the repentant flock raised an equestrian statue that was very good in the park.

thus, in the future, every time that black sheep appeared they were quickly passed by the arms so that the future generations of common sheep could also be exercised in the sculpture