How a person responds to a question that they don’t know the answer to tells you quite a bit about what kind of person they are. Some people try desperately to hide their lack of knowledge by rambling or even making up facts. Sometimes, people will become very defensive and heatedly argue a point even if they are not sure it is the right answer or not, attacking the person asking the question (ad hominem argument).
The model answer would be to admit that you don’t know the answer. A marker of a well-adjusted person is their ability to admit that they are imperfect, as well as an openness to continue learning to keep filling their gaps of knowledge.
The world is an extremely vast place and our sphere of knowledge is rapidly expanding in the age of information. It is impossible to know everything in the world and it is arrogant to assume that you can.
Furthermore, knowledge changes with time. Facts and paradigms once deemed to be concrete have faltered with new evidence. New concepts such as the theory of evolution and the Big Bang were shunned initially, but are now basic knowledge that best explain what we observe. Without an openness to learn and change our minds, we would become stagnant and boring.
No one likes to be wrong or perceived as stupid. But if we let our pride get in the way, we could never improve and grow. It is okay not to know the answer, as long as you are open to learn.