Well, using my limited knowledge, "cleaving" means to chop, break in half, split, etc. Twain means twice. So, perhaps it's like "you've broke my heart in half", something along those lines? hopefully this helps you.
Answer:
the form of a poem is units of spoken language
Personification is adding human characteristics to a non-human object. (D. "The landscape listens, shadows - hold their breath.") The landscape listening as if it has ears, and shadows holding their breath are things a living thing would do, so (D) is the best answer.
It would be imperative because it shows vital importance