The two main different ways to address people are formally and

formally and informally.

Explanation:

In Spanish, we distinguish two ways of addressing someone: formally and informally.

When talking to a friend, we use the pronoun tú. We must also use the verb conjugated in the second person plural, while if we refer to a group of two or more friends, we use the pronoun vosotros, and the second person plural form for the verb. This is informal address.

However, when we talk to a teacher, an elder, a boss or whomever we want to be respectful towards, we use the pronoun usted, which uses the third person singular form of the verb, while if there are two or more of our interlocutors, we use ustedes, and the third person plural form of the verb. This is a way to address somebody formally.

b.

explanation:

just because.

well, the b sentence is the only one that has sense.