A 35-year-old man with a history of opioid use disorder using illicit fentanyl presents seeking help to stop. According to the updated Canadian guideline on opioid use disorder, what is the preferred first-line treatment?AInpatient detoxification with short-term clonidine onlyBOpioid agonist therapy with buprenorphine or methadoneCAbstinence-based residential programme without medicationsDNaltrexone oral monotherapy as first-lineENo treatment is recommended; advise him to reduce use graduallyCheck my answer