I'm interning at a company, and I have a new project. After my manager explained it to me, I went to my desk, researched it a bit and mulled it over, then returned to his office:
Me: "So for this project, I guess I should do Thing A?"
Manager: "Why would you do Thing A? That doesn't make sense. You should talk to Guy. He deals with this type of thing. He can help you get started."
So the next day, I talked to Guy:
Me: "Guy, Manager told me you would be able to help me. How should I start this project?"
Guy: "If I had to do a project like this, I would start by doing Thing A."
My dilemma how can I go back to my manager and getting him to sign-off on doing Thing A. How can I present this to him without coming across as combative or adversarial? I don't want to prove him wrong; I just want to do a good job.