Hello I am a Spanish speaker and would like to help you with these answers. So, let's start:
1. Señores, ¿dónde ____________________ Uds.? (trabajar)
This is an Spanish question in the present form. In Spanish, the simple present tense (el presente or el presente de indicativo) is used to talk about habitual actions, routines, things happening now or in the near future, universal truths, facts, hypotheticals, lapses of time, and for ordering in restaurants and stores. So we need to conjugate the verb trabajar for the second-person plural (formal ustedes), so this conjugation is trabajan, so the right answer is:
Señores, ¿dónde trabajan Uds.?
2. More than one teacher
The correct answer is ustedes. We use this subject pronoun for the second-person plural. It's a formal way to address someone. Recall that subject pronouns are pronouns that identify who or what is performing the action of a verb. For instance:
Hola profesores, ¿ustedes vendrán a la escuela mañana? (Hello professors, will you come to school tomorrow?)
3. Your best friend
The correct answer is tú. We use this subject pronoun for the second-person singular. It's an informal way to address someone. So, this sentence is an example:
Hola amigo, tú deberías venir a mi casa (Hello my friend, you should come to my house)
4. Choose the correct translation: you (formal)
The correct translation is usted. We use this subject pronoun to address someone in a formal way. For instance, a principal, a priest, a ruler, a person who we don't know, among others.
5. Whom would you not address using the tú form?
Since the subject pronoun tú is an informal way to address someone we would not address a principal using this pronoun. So the right answer is c. a principal
6. In which situation would you most likely address someone using the tú form?
As we said, tú is an informal subject pronoun. So, the situation we would most likely address someone using the tú form is in b. meeting a fellow student on the first day of school.
Even though we don't know that student it is allowed to use an informal way to address him or her. This is true because of the context of the situation, that is, the school. So, among students, it is allowed to address in an informal way.
