Final answer:
The correct verb to complete the sentence is 'hacen'. The sentence means 'We are sixteen years old and today is our birthday.'
Step-by-step explanation:
The correct verb to complete the sentence is 'hacen'. In the sentence 'Tenemos dieciséis años y hoy es nuestro cumpleaños', the subject is 'nosotros' which means 'we'. Since 'we' is a plural pronoun in Spanish, we use the plural form of the verb 'hacer' which is 'hacen'. This sentence means 'We are sixteen years old and today is our birthday.'
Learn more about verb conjugation in Spanish