The correct answer is C. This passage from Shakespeare's work clearly shows a situation in which Richard III uses the soliloquy as a foreshadowing tool to anticipate the reader about his plans for his brother and sister-in-law.
A soliloquy (from Latin solo "to oneself" + loquor "I talk") is a device often used in drama when a character speaks to him- or herself, relating thoughts and feelings, thereby also sharing them with the audience, giving off the illusion of being a series of unspoken reflections. If other characters are present, they keep silent and/or are disregarded by the speaker. Though it should be said that sometimes, depending on the performance, a monologue that is written as a soliloquy, will be addressed directly to the audience. And sometimes it is hard to tell if what is being heard is a monologue, or a duologue or a soliloquy; in which case choosing the right term may be a matter of interpretation.