Final answer:
The correct verbal form is 'O nos faltan' which means 'we are missing'.
Step-by-step explanation:
The correct answer is O nos faltan which means 'we are missing'. In this sentence, 'a nosotros' is the indirect object and 'los protectores para las piernas' is the direct object. The verb 'faltan' agrees with the subject 'nosotros' and is in the third-person plural form to match the plural direct object.
Learn more about Verb conjugation in Spanish