Answer:
According to Mary Shelley's 1831 introduction, where did she get her inspiration for Frankenstein? Mary Shelley was only 18 when she began writing Frankenstein. Her parents were both well-known writers. ... The idea both frightened her and inspired her ghost story, which later became Frankenstein.
'Before they ate a snack' is the correct answer, it is the adverbial clause of time. A cannot be correct because that is an independent clause, and adverb clause has to be dependent. B isn't a clause at all.
D, Was is the answer, a being verb is showing the state of being such as (am, is, are, was, were, be, being, been.