Question

Yo siempre _______ la verdad.

Answer 1

Yo siempre digo la verdad.

You can use any form of the verb, but it has to be indicative. I have used the present form (the most used in these cases) of the verb "decir" (say).

MissSpanish

Answer 2

Answer:

Digo.

Explanation:

Yo siempre digo la verdad.