Final answer:
The best verb to complete the sentence is 'digas' which means 'you say' in English.
Step-by-step explanation:
The best verb to complete the sentence is digas which means 'you say' in English. The sentence would then be 'Yo siempre digas la verdad.' The verb 'digas' is the second person singular form of the verb 'decir' which is used to express actions and statements.
Learn more about Verb conjugation in Spanish