As an undergraduate, I volunteered to present part of a another student's Ph.D. work at a tech conference. Like you, I was most nervous about questions because

As an undergraduate, I volunteered to present part of a another student's Ph.D. work at a tech conference. Like you, I was most nervous about questions because it wasn't my research and I wasn't even a grad student, so I was afraid that I would lose my credibility with the audience if they questioned me too closely. But I decided to just go in with confidence, and I learned all I could about the research I was presenting. My talk was at the end of a long day, and due to a poorly organized conference, most of the potential audience had gotten fed up and gone home before I even got a chance to give my talk. In the end, I gave the talk to a nearly empty room and no one asked any questions.