Visa application rejected

My parents went to Chengdu for their first visa interview, but were rejected.

Five questions were asked:

VO: Why do you want to go to US?
Parents: To attend my daughter's graduation ceremony.

VO: Have you been to US before?
Parents: No

VO: when will you go to US?
Parents: Next March

VO: How many kids do you have?
Parents: 3

VO: Show me your house title.
Parents: sumbit one

Then VO rejected their application.