Answer:
The correct answer is han dicho.
Explanation:
In this case we are faced with verb tense pretérito perfecto.
We use it to express actions that occurred in the past and extend to the present, and actions that happened in the past and that have as a consequence a situation or result related to the present or the future.
To conjugate a verb in the past perfect we use the auxiliary haber in present and the participle of the main verb.
Yo he dicho
Tú has dicho
Él/Ella/Usted ha dicho
Nosotros/as hemos dicho
Vosotros/as habéis dicho
Ellos/Ellas/Ustedes han dicho
