Answer: C. a boggy type of land
Explanation: Quagmire is a word that refers to a soft, wet and spongy ground, usually a boggy type of land. The context of the excerpt of Hawthorne's biographical sketch of Ben Franklin doesn't provide enough information to specify the exact meaning of the word in that section, but generally, the term quagmire is used to refer to a difficult or precarious situation or a problem, but it's also used to refer to a wet and spongy ground.
(this answer i am not so sold on it, but i think it's the right answer)