<h2>
Answer:</h2>
In this exercise, we must choose the correct Spanish subject pronoun. In order to understand this problem, let's provide the list of subject pronoun:
Yo - I
Tú - You
Él/ella - He/she
Nosotros - We
Vosotros - You (Informal)
Ustedes - You (formal)
Ellos/ellas - They (masculine) / They (feminine)
<h3>
El Señor Díaz:</h3>
Addressing him: Usted
El Señor Díaz means Mr. Díaz, so you address him in a formal way. Hence use usted
Talking about him: él
If you talk about him, you use the third person singular él
___________________________
<h3>
Jimena y Marissa:</h3>
Addressing him: Vosotras/ellas
In Spain it is common to use vosotras in informal way and ustedes in a formal way. In other Spanish speaking countries is common to use ustedes in both forms.
Talking about him: ellas
If you talk about them, you use the third person plural ellas
___________________________
<h3>
Maru y Miguel:</h3>
Addressing him: Vosotros/ustedes
Unlike the previous case, we use vosotros because Maru y Miguel are a group of people, so we use the masculine form. Ustedes doesn't change according with gender.
Talking about him: ellos
If you talk about them, you use the third person plural ellos
___________________________
<h2>
THE REST OF THE EXERCISES ARE SIMILAR:</h2><h2 /><h3>
La profesora:</h3>
Addressing him: Usted
Formal form because she's a teacher, so use usted
Talking about him: ella
Use the third person singular ella
___________________________
<h3>
Maru y Miguel:</h3>
Addressing him: Vosotros/ustedes
Unlike the previous case, we use vosotros because Maru y Miguel are a group of people, so we use the masculine form. Ustedes doesn't change according with gender.
Talking about him: ellos
If you talk about them, you use the third person plural ellos
___________________________
<h3>
Un estudiante:</h3>
Addressing him: tú
You use the informal form because he's your classmate.
Talking about him: ellos
You use the third person singular él
___________________________
<h3>
el director de una escuela:</h3>
Addressing him: usted
He's the school principal, so you must show respect and use usted
Talking about him: él
You use the third person singular él
___________________________
<h3>
Tres chicas:</h3>
Addressing him: vosotras/ustedes
Explained above
Talking about him: ellas
As mentioned, you use the third person plural ellas
___________________________
<h3>
Un pasajero de autobús:</h3>
Addressing him: usted
You don't know that passenger, so use the formal form usted
Talking about him: él
Use the third person singular él
___________________________
<h3>
Juan Carlos y Felipe:</h3>
Addressing him: Vosotros/ustedes
Use either vosotros or ustedes depending on whether you need to show respect or not
Talking about him: ellos
Use the third person plural ellos