Subject Pronouns or Personal pronouns in Spanish (similar to English) are used to refer to people, animals or objects and express different grammatical categories. In addition they are useful to distinguish the grammatical number and grammatical gender in a sentence:
1st person singular I: Yo
2nd person singular You: Tú (informal)/ Usted (formal)
3rd person singular He/She/It: El/Ella/eso/esa
1st person plural We: Nosotros
2nd person plural You: Ustedes (In latinAmerica) / Vosotros (In Spain)
3rd person plural They: Ellos/Ellas
According to this, let's begin with the answers:
1. mi hermano y yo (my brother and I) refers to the 1st person in plural masculine, hence the corresponding subject pronoun is:
2. tu amigo y tú (Your friend and you) refers to the 2nd person in plural masculine, hence the corresponding subject pronoun is:
3. el profesor (the teacher) refers to the 3rd person in singular masculine, hence the corresponding subject pronoun is:
4. mis compañeros de clase (my classmates) refers to the 3rd person in plural masculine, hence the corresponding subject pronoun is:
5. unos chicos y unas chicas (some guys and some girls) refers to the 3rd person in plural masculine , hence the corresponding subject pronoun is:
The spanish verb ser (to be) is conjugated as follows:
1st person singular Yo: soy
2nd person singular (informal) Tú: eres
2nd person singular (formal) Usted: es
3rd person singular Él/Ella/eso/esa: es
1st person plural Nosotros: somos
2nd person plural Ustedes (In latinAmerica): son
2nd person plural Vosotros (In Spain): sois
3rd person plural Ellos/Ellas: son
Knowing this, let's answer the questions:
Marisa and Felipe corresponds to the 3rd person plural ellos (they), hence the correct conjugation of ser is ellos son.
Tus amigos y tú (Your friends and you) corresponds to the 2nd person plural ustedes (you), hence the correct conjugation of ser is ustedes son.
Yo (I) corresponds to the 1st person singular, hence the correct conjugation of ser is Yo soy.
Mi computadora (My computer) corresponds to the 3rd person singular feminine esa (it), hence the correct conjugation of ser is esa es.
Los chicos de mi clase y yo (The guys in my class and I) corresponds to the 1st person plural nosotros (we), hence the correct conjugation of ser is nosotros somos.
