From Vygotsky's Perspective, What Important Role Does Inner Speech Play

From Vygotsky's perspective, what important role does inner speech play?

A) By giving ourselves directions about what to do next, we guide ourselves through complex tasks.
B) By practicing linguistic structures mentally, we develop more complex language capabilities.
C) By using words mentally as well as orally, we develop a more abstract representation of the world.
D) By talking to ourselves about what we should have done or said in a particular situation, we remember that situation more vividly.