Are you willing to relocate or work at remote sites?

Be honest. If you have a real constraint, say it now rather than after the offer.

Model answer.

What the interviewer wants. Core and PSU roles often involve power plants, substations, refineries, construction sites or mines, which may be far from cities. Shift work is normal in plant operations. The interviewer is checking whether you will accept the posting and stay, or leave after a few months.

If you are genuinely willing
Say yes clearly, and show that you understand what it means:
"Yes. I understand that much of the core work in this field happens at plants and project sites, not in city offices, and that's where I'll learn the most in the first few years. I've [relevant experience, if true: e.g. done my internship at a substation/site and stayed near it for six weeks], so I have some idea of what site life is like. I'm also comfortable with shift duty."

If you have a real constraint
Do not say yes just to get the offer and then refuse the posting. That damages trust and may cost you the job anyway. State the constraint briefly and show flexibility where you can:
"I'm willing to relocate and work in shifts. The only consideration I have is [real reason, e.g. a parent's ongoing medical treatment]. If there is any flexibility in the first posting, I'd appreciate it, but I understand that postings depend on the organisation's needs."

Tips

• Do not over-promise ("I'll go anywhere, any time, forever"). It sounds rehearsed.
• Do not ask about the posting location or transfer policy as your first question. Ask about training and the type of work first.
• If you have preferences, it is fine to mention them briefly when asked, but show that you will accept the company's decision.

Common mistake. Saying yes in the interview and then declining the joining letter because of the location. Companies remember this, and it can affect campus relations for your juniors.

Likely follow-up. "How will your family feel about it?" Answer honestly. If you have discussed it with them, say so.