Answer:
1. Dice/Dicen que aprender a esquiar no es muy difícil. 2. Receta/Recetan los antibióticos demasiado. 3. Necesita/Necesitan enfermeras bilingües. 4. Daño/Dañaron el auto anoche.
Explanation:
Phrases do not present any pronoun and there are several choices by assuming one, most common singular and plural pronouns were used (el/ella/ellos/ellas).