4. Conjugate the verb according to who is in each sentence.

Los estudiantes (Leer) libros en la clase.

O leo
O leemos
O leen

Los estudiantes leen libros en la clase.

The correct conjugation of the verb "leer" in each sentence is:

Yo leo
Nosotros leemos
Ellos leen

To conjugate the verb "leer" according to who is in each sentence, you need to consider the subject pronouns and the corresponding verb endings in Spanish.

The subject "Los estudiantes" refers to the third-person plural (they), so we need to use the conjugation for "they" in the present tense.

The correct conjugations for "leer" in the present tense are:

- "leo" for the first-person singular (I)
- "leemos" for the first-person plural (we)
- "leen" for the third-person plural (they)

So, the correct answer is:

Los estudiantes leen libros en la clase.