The other answer doesn't really give a good explanation of how to actually resolve the situation.
From a previous answer of mine:
How can I develop the confidence to answer questions like:
There is no magical "instant confidence" anyone can give you.
I know you cannot answer these questions for me but I do not know how to prepare good responses for these types of questions, and then
deliver them with confidence during the interview.
You need to practice.
If you've been at the same company your entire career you probably
have interviewed only a handful of times and not at all recently.
Unless interviewing comes naturally to you, you won't feel comfortable
at all, and if your only opportunities to interview come in the actual
interviews which happen only once every few years, you'll never
develop the skills to do so (especially if you don't feel confident in
the first place).
You need to practice answering them. Do this in three steps.
- Find lots of questions like that which are hard for you to answer. The Internet makes this really easy
- Write out short answers to them
- Have people (family, friends, Toastmasters, a rubber
or the wall) ask you them and get familiar answering them
This is all just as relevant here.
From your comment and more specifically for your situation:
but just a thing to know that how much time delay be accepted between the question and the answer
You can take time to answer questions. You do not have to respond immediately. You can take time to think through them - seriously. I've had offers for jobs where I was asked something, and took some time to think and said something like, "let me think for a bit" and spent a few seconds thinking.
Generally this is not seen as a bad thing at all.
If this is a serious problem for you to actually do in interviews, teach yourself to count to 1 after every question you get asked - say "one-one-thousand" in your head each time you get asked a question. If this isn't enough make it a bit longer (and you can say whatever you want, really, you could say "I can totally answer this - I'm not nervous!" if you think this helps).
Find a friend who knows your technical knowledge and have them ask you questions of things you don't necessarily know to get used to this. Dress up as if you are interviewing if you want.
The overall point is - you won't magically get better at interviewing and high stress situations without some practice.