Final answer:
The term 'thou' in the Shakespearean context, especially from the play 'Macbeth', refers to a ghost that appears and significantly affects the plot and characters.
Step-by-step explanation:
The passage 'Thou comest in such a questionable shape' is a line from William Shakespeare's iconic play, Macbeth. Within the context of this play, the word 'thou' typically refers to a character being directly addressed by the speaker. In this instance, given the options provided and the thematic elements of Macbeth, which includes supernatural appearances and visions, the correct answer is that 'thou' refers to a ghost. The play is renowned for its exploration of ambition, power, and the supernatural, featuring ghosts and apparitions that have significant roles in the development of the plot and the psychological state of the characters.