Final answer:
The effect of the underlined passages best described is a sense of dread and foreboding. The literary excerpts use dark, ominous imagery to convey a nightmarish atmosphere, aligning with option (a).
Step-by-step explanation:
From the provided excerpts taken from various literary works, including George MacDonald's 'The Somnambulist', it is evident that the underlined passages evoke a sense of unease, trepidation, and an ominous atmosphere.
The descriptions are rich with imagery that conveys dread, foreboding, and distress, such as 'tortured into motion by the breath of a rising tempest' and 'an incubus of utterly causeless alarm'. These examples illustrate a surreal, nightmarish quality where the protagonist experiences a profound sense of horror and discomfort.
The correct option in response to the effect described by the underlined passages is (a) The protagonist experiences a sense of dread and foreboding. This is clearly represented by the anxious and fearful tone of the passages, unnerving descriptions, and the characters' reactions to their environments, which are fraught with psychological disturbances and dark, unsettling imagery.