Answer:
Se dice*
Step-by-step explanation:
When you are using passive boice in spanish, you need to add "se" before the verb and conjugte the verb in the singular third person form, for example "Hacerse" would be se hace so for decirse we conjugate this way
Yo digo
Tu dices
Él/Ella dice
So the singular third person for the verb decir would be dice, and you just put before the "Se", so it would be se dice.