Right answer: Nosotros se las mandamos
This is a good example of the usage of se as an indirect complement, in order to substitute the Indirect Object Pronouns 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 who?) Or ¿para quién? (for whom?)
In the case of the sentence Nosotros mandamos las manzanas a ellos (We send the apples to them) if we ask ourselves the following question:
¿A quién le mandamos las manzanas?
Who do we send the apples to?
The answer is:
A ellos
To them
Being ellos (them) who indirectly receives the action, therefore the indirect complement of the sentence.
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 Nosotros mandamos las manzanas a ellos, knowing that the indirect object is ellos, which is the 3rd person plural; the indirect object pronoun in Spanish is les.
In that way the initial sentence changes to:
Les mandamos las manzanas (a ellos)
We send the apples (to them)
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 las is used because the direct object is las manzanas (the apples) that are feminine and plural, therefore the sentence:
Nosotros mandamos las manzanas a ellos
Changes to:
Nosotros se las mandamos
Which is finally the right answer.
