Maintain a positive attitude when being asked questions designed to uncover something negative about your education or coursework. Put a positive spin on your response and address how you learned and grew from this tough engineering course despite high levels of difficulty. Talk about how other strengths balance things out and your intention to strengthen any skill required to be successful at this position. The interviewer may also want to discuss what kind of training you'd be open to in the future. Where you're engineering education is headed is as important as where you are.