For this case we can translate the sentence as:
Juanito's father demands that his son __________ his homework with excellence.
We must complete the sentence with the verb "to do" in the present and third person. That is to say: El haga
Thus, the sentence looks like:
Juanito's dad demands that his son do his homework with excellence.
Answer:
Option B
El papá de Juanito exige que su hijo haga sus tareas con excelencia.