The correct option is B uncomfortable
The passage explains about the nature of the De Coninck sisters who were born melancholiac. There behavior would swing from one extreme to the other and the witness of both the sides of their nature was an elderly female servants. In the privacy of their rooms where they were not the life of the party, they would give into a deep sadness- "They would talk, then, of life with the black bitterness of two Timons of Athens...". The atmosphere that was a result of this behavior was very caustic- an atmosphere that would make somebody else uncomfortable - not concerned or preoccupied or any of the other given choices. In the given context, 'uncanny' most nearly means uncomfortable. Option B is our answer.