51 A clinical trial involves patients with a diagnosis of cancer who have intractable nausea as a result of chemotherapy. The patients are divided into two groups; one group is given a placebo, and one group is given a drug. The group receiving the drug is found to have reduced self-reported nausea and diminished weight loss compared with the placebo group. The patients receiving the drug seem to have no major adverse side effects. Of the following agents, classified as drugs of abuse in parts of the world, which is most likely to have the beneficial effects found in this study? (A) Barbiturate (B) Cocaine (C) Heroin (D) Marijuana (E) Methylphenidate (F) Methamphetamine (G) Phencyclidine