The Adventures of Sherlock Holmes by Sir Arthur Conan Doyle

When I glance over my notes and records of the Sherlock Holmes cases, I am faced by so many that present strange and interesting features. It is no easy matter to know which to choose and which to leave. Some have already gained publicity through the papers. Some have baffled his investigative skill and would be, as narratives, beginnings without endings. Others have been but partially cleared up and have their explanations founded rather upon guesswork and deduction than on that absolute logical proof, which was so dear to him. There is, however, one of these last that was so remarkable in its details and so startling in its results. I am tempted to give some account of it in spite of the fact that there are points in connection with it that never have been, and probably never will be, entirely cleared up.
5
Read this sentence from the passage.

I am tempted to give some account of it in spite of the fact that there are points in connection with it that never have been, and probably never will be, entirely cleared up.

How does this sentence contribute to the tone of the passage?
A.
It creates an enraged tone by making the reader feel frustrated.
B.
It creates an amusing tone by showing the author's eagerness to share partial details of unsolved cases.
C.
It creates a thrilling tone by generating a sense of anticipation.
D.
It creates a humorous tone by explaining the author's incapability of revealing all the case details to the reader. Help PLsss!