This is just my two-cents.
It is all about you. If you don't know the answer to something, just say that you are unsure. If you have a small idea on how it works, let the interviewers know what you think the answer might be.
Sometimes, I feel that it is the human touch that matters. The fact that you are able to say that you do not know and let everyone move on from there. Heck, the interviewer might even tell you the answer and you guys can continue to have a discussion.
Again, this is my opinion and it may be against the "best practices" of interviews out there.