The correct option is B Sarcastic
The tone used by the author in the last sentence of the passage is sarcastic. From the concluding line ‘..No villain had done this thing: it was the work of ladies and gentlemen who were rich and often clever..’, we get a hint. Also, the passage is not mournful; hence the tone cannot be lamenting. Neither does the passage support one cause which leads to another, so it cannot be labelled as complimentary. Confusion can arise between sarcastic and ironic. Irony is something that exists because of the existence of two opposite situations; the last line certainly does not highlight any such situation and this helps us rule out this answer option.