Answer:
"I'm book-learned enough for that; but a man has his feelings, and I give you my bible-word it was Mr. Hyde!"
Step-by-step explanation:
Robert Louis Stevenson's "The Strange Case of Dr. Jekyll and Mr. Hyde" revolves around the story of a good doctor and his struggle to contain his monstrous alter ego. The story deals with themes of good vs. evil, morality, loyalty, etc.
Another important theme of the story is to always trust one's instincts. This is evident in the line "I'm book-learned enough for that; but a man has his feelings, and I give you my bible-word it was Mr. Hyde!" uttered by Poole, the butler of Dr. Henry Jekyll.
In his speech/dialogue, we can know that Poole is sure of his instinctive belief that Hyde was responsible for the murder of Dr. Jekyll. He insists that "his feelings" tell him the murderer was Mr. Hyde.
Thus, the correct answer is the third option.