Related to "confidence": you should be completely comfortable with your material. In fact, you should have mastery over it.

Nothing kills a presentation faster than someone in the audience asking "where did you get that number / equation / data?" or "why did you choose that technology / layout / structure?" and the presenter not knowing. People aren't going to trust you with their money if you don't understand what you're telling them well enough to answer probing questions.

I had a professor in college who, unlike many professors in college, had actually worked for a living. He imparted on me the following panacea for all questions you cannot answer (not related to the startup context but I think you can make it work): "That's a good question which deserves a more thorough answer than the one I'm prepared to give you off the top of my head. Let's follow up on it later."

It suggests that you have sufficient confident mastery of the field to know that you don't know the answer off the top of your head but that somebody on the team has a satisfactory answer, suggests you know the answer isn't a threat to you, and allows you to control the pacing and direction of the presentation.

That answer and its brethren are very good answers. However, they become progressively less useful each time you use them in the same presentation. They are useful when you essentially do have mastery over your material, and you will therefore not need to dodge most questions with them. In fact, they are useful because, if used in the most sincere and literal way, they are a compliment to the person who asked the insightful question.

(Of course, they are bad answers to the basic question about provenance asked by the GP - if someone was asking you where you got Graph X and you don't know, telling them that you'll talk with them later will be treated as the dodge that it is, not as a compliment.)