This is a good example of the usage of se as an indirect complement, in order to substitute the indirect complement le or les.
What does this mean?
Let’s begin by explaining that the Indirect Complement of a sentence is the person, animal or thing that indirectly receives the action of the verb.
To identify it in a sentence, we must ask to the verb ¿a quién? (to whom?) Or ¿para quién? (for whom?)
In the case of the sentence (Yo) Voy a leer el periódico a Roberto (I'm going to read the newspaper to Roberto) if we ask ourselves the following question:
¿a quién voy a leer el periódico?
(To whom am I going to read the newspaper?)
The answer is:
A Roberto
(To Roberto)
Being Roberto (him) who indirectly receives the action
Now, the Indirect Object Pronouns replace a word or phrase, which in the sentence fulfills the function of indirect object.
They are written before the verb, when it is conjugated.
These pronouns are listed below:
1st person singular Yo: me
2nd person singular (informal) Tú: te
2nd person singular (formal) Usted: le
3rd person singular Él/Ella/eso/esa: le
1st person plural Nosotros: nos
2nd person plural Ustedes (In latinAmerica): les
2nd person plural Vosotros (In Spain): os
3rd person plural Ellos/Ellas: les
Then, returning to the sentence Voy a leer el periódico a Roberto, knowing that the indirect complement is Roberto, who is the 3rd person singular Él (he); the indirect object pronoun in Spanish is le.
In that way the initial sentence changes to:
Le voy a leer el periódico (a Roberto)
I'm going to read the newspaper (to Roberto)
This is where the personal pronoun se comes in, as an Indirect Complement, and replacing le or les (indirect object pronouns), immediately followed by one of the following pronouns depending on the direct object:
lo (singular masculine)
la (singular femenine)
los (plural masculine)
las (plural femenine)
In this case lo is used because Roberto (he) is masculine and singular, therefore the sentence:
Le voy a leer el periódico a Roberto
Changes to:
Se lo voy a leer
Which is finally the right answer.
