Step 1: After implanting the donor liver in orthotopic liver transplantation, biliary continuity must be restored so bile drains into the gut.
Step 2: The preferred reconstruction is a direct duct-to-duct anastomosis (donor common bile duct to recipient common bile duct, choledochocholedochostomy). This is physiological, preserves the sphincter of Oddi, and keeps endoscopic access to the biliary tree for later stenting if needed.
Step 3: When duct-to-duct is not feasible, for example with a diseased or absent recipient duct (as in primary sclerosing cholangitis) or a large size mismatch, a Roux-en-Y choledochojejunostomy (hepaticojejunostomy) is used instead.
Step 4: Option A captures both the first choice and its standard backup, so it is the best answer. Anastomosis to the duodenum (option B) is not standard. A plain loop jejunal anastomosis without a Roux limb (option C) risks reflux cholangitis and is inferior. Routine external drainage then later surgery (option D) is not the preferred primary plan.
Conclusion: The correct answer is A. Donor duct to recipient duct or Roux-en-Y choledochojejunostomy.