This is very straightforward. If the junior was raising objections with actual meat on them, it behooves you to act professionally, say you don't know, and put it on the agenda for the next meeting.
The reasoning here is as follows:
If anybody brings up a serious objection, the client is going to want to see resolution.
If you are not able to offer resolution immediately, you have two basic options:
Try to bluff your way through, or otherwise discount the issue. This will not look good to a client. They want resolution. You have effectively ended negotiations by refusing to provide resolution.
Shelve the issue. This offers the promise of resolution, even if it isn't currently forthcoming. This offers you the opportunity to continue the meeting, discussing the rest of the business you met to deal with. This is a productive use of time for everybody involved. It is also assumptive. You're communicating "We'll tell you next time." This is effectively a compromise. "We can't give you resolution now, but we can give it soon." They may take it or leave it. That is still better than the alternative. It is also a promise. Making and keeping promises is the way to earn trust.