“It is impossible to say how first the idea entered my brain; but once conceived, it haunted me day and night.”

What does this line signify?

A) In this line, the narrator hints at the events to come.

B) In this line, the narrator talks about how his brain is not functioning properly.

C) In this line, the narrator informs the readers about his sanity problems.

D) In this line, the narrator informs that he is unable to speak.