Answer:
1.- Guillermo es el mayor de los hijos
2.- Alejandro es el más paciente de los primos
3.- El jugo es el más dulce de las bebidas
4.- Pau Gasol es el mejor de los jugadores
Explanation:
I'm a native speaker
The situation: The air pollution is so bad that the city council is thinking of banning the use of cars in the city on alternate days, depending on the last number on the license plate of the car (even numbers on Mondays, Wednesdays and Friday, odd numbers on Tuesdays, Thursdays and Saturdays)
What should state officials do?
What should local officials do?
What should local citizens have done to maintain and improve the condition of the places?
Oído.
Since the infinitive verb is oír, which stems ends with a vowel (i in this case), we replace the inifinitive part ir with oído. Remember to include the accent since its an irregular form.