Answer:
The right answer in each case is:
- Correcto.
- Incorrecto.
- Vendiste. 
Step-by-step explanation:
The translation of the answers is:
- Right. 
- Incorrect. 
- You sold.
In each of the cases, the answers were chosen due to the following explanation: 
- "El niño" is a noun that could be replaced by the personal pronoun "él," and the right conjugation of the verb "escoger" in the Preterite Form for that noun is "escogió." 
- The personal pronoun used in the sentence is "yo," and the right conjugation of the verb "anunciar" in Preterite Form for that noun is "anuncié." 
- The conjugations of the verb "vender" in Preterite Form taking into accoun the personal pronouns are: 
- Yo vendí. 
- Tú vendiste. 
- Usted vendió. 
- Él vendió. 
- Ella vendió. 
- Ello vendió. 
- Nosotros/Nosotras vendimos. 
- Ustedes vendieron. 
- Ellos/Ellas vendieron. 
How the personal pronoun used in the sentence is "tú," the right conjugation is "vendiste."