The correct option is D Keeble is attempting to appear casual.
Option D is the correct answer. Mr. Keeble had been preparing what he had wanted to say to his, and was fully aware of the sensitivity of the subject, and the impact it would have on the latter. His speech was rehearsed and his attempt to be forcefully casual is apparent by the way he directly approaches his wife on the matter. Options A,B,C and E are incorrect in context of the text because he does indeed know and discloses the location to his wife. There is no mention of him failing his memory. Thus, The other options are incorrect.