Thanks for all your suggestions and ideas. My parents successfully got visa in chennai consulate.
Qns asked: [All questions were asked to my dad only.]
1) What is you son doing in US. ?
2) When did he go to US ?
3) What are you doing in India. ?
Small Time Business
4) Is your son married ?
5) Do you have Grandchildren in india ?
Please pay fees in counter xyz.
Good Luck to All.