1. Stay calm: First of all, don't panic. Take a deep breath and give yourself time to think. Keeping calm helps you to answer questions better.

2. Ask for clarification: If you are not sure about the interviewer's question, don't guess. Politely ask them to repeat or clarify the question. This will give you more time to understand the question and may help you find the right answer.

3. Answer honestly: If you really don't know the answer, tell the interviewer honestly. Explain your scope of knowledge and your confusion. Interviewers usually appreciate your honesty and frankness.

4. Change the subject: If you feel unable to answer a question, you can try to change the subject. For example, you can say, "This is an interesting question, but I don't know how to answer it. Tell me more about my experience in other fields. " This will help you avoid getting into trouble on a certain problem.

5. Show your problem-solving ability: Even if you can't answer questions directly, you can show your problem-solving ability. For example, you can describe how you analyze problems, seek information or cooperate with others to solve problems.

6. Suggest follow-up: If you really don't know the answer, but know how to find it, you can suggest finding relevant information after the interview. This will show that you are willing to work hard to solve the problem.

In short, when you can't answer in the interview, it is the key to stay calm and frank, show your problem-solving ability and ask for clarification. At the same time, don't forget to show your communication skills and teamwork spirit during the interview.