When you present together with others, you need to align upfront who will address questions from the audience. This is especially important when you have a dedicated Q&A session.
In various cases it will be obvious who will address the question, for example it is the person who addressed this topic during the presentation or if the question is specifically addressed to one of the presenters. If a question is specifically addressed to one person this persons should start with answering the question, however others may add to the answer.
You should agree what to do when it is not obvious who should address the question. Maybe using some signals as for example putting your hands behind your back when you have no answer / nothing to comment on the question and put your hands in front of you when you have something to say about it, so it is clear for the other presenters who will answer or takes the lead in addressing the question. In the book that is part of the public speaking kit, you will find multiple tips about how best to address questions from your audience.