Which of the following sentences could take the place of: Yo dije la verdad a mi madre./ Se la dije. / Le la dije. / La se dije.
Answer : Se la dije.
Explanation : The indirect object points out to the receiver of the action of the verb and the direct object concretes the action of the verb. In this sentence the direct object is "la verdad" and the indirect object is "mi madre". The pronoun "se" is an invariable pronoun that substitutes the indirect object as a variant of "le", when it is followed by another pronoun. The pronoun "se" does not change in terms of number or gender, unlike the direct object pronoun that does indicate gender and number, which is why the direct object pronoun has the same gender and number as the word it replaces, which it is "la verdad", which is a singular feminine noun and is replaced by "la". Then the combination of indirect object pronoun + direct object pronoun results: Se => mi madre + la => la verdad.