You are answering a USMLE-style medical question. Question: A 53-year-old man with recurrent pancreatic adenocarcinoma is enrolled in a clinical trial for a novel chemotherapeutic agent that his physician believes may be beneficial to his condition. The novel drug was previously tested in a small population and is now undergoing a larger phase 3 trial in preparation for FDA approval. A dose-response trial had the following results: 10 mg dose - 6/59 patients demonstrated improvement 20 mg dose - 19/49 patients demonstrated improvement 30 mg dose - 26/53 patients demonstrated improvement 40 mg dose - 46/51 patients demonstrated improvement The same trial also had the following safety profile: 20 mg dose - 5/49 patients had a treatment related adverse event 40 mg dose - 11/51 patients had a treatment related adverse event 60 mg dose - 15/42 patients had a treatment related adverse event 80 mg dose - 23/47 patients had a treatment related adverse event 100 mg dose - 47/52 patients had a treatment related adverse event Based on this study, which of the following represents the most likely therapeutic index for this novel chemotherapeutic agent? Options: A) 0.375 B) 0.5 C) 2.5 D) 2.67 Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.