The correct answer is talk to oneself.
A. talk in one's sleep
B. write about the past
C. talk to oneself
D. sing without accompaniment
The correct answer is [C] To talk to oneself (a device often used in plays); to deliver a soliloquy; to speak one's thoughts aloud in solitude.
Soliloquize comes from Latin solus (alone) and loqui (speak).
Examples of use:
- She soliloquized at length about the nature of love.
- His role required him to soliloquize several times during the play.