Applied for Parents US Tourist VISA

I have applied for the US Tourist Visa of my parents and their embassy interview is scheduled in mid of June 2018. I want to know about the documents to be needed at that time and questions they may ask.

Thanks.

Evidence that they are in excellent health

Evidence that they have international health insurance coverage

Evidence that they have strong family ties in home country

Evidence that the person they are visiting is himself / herself a non-immigrant with no permanent ties to USA such as H1B, L1 or F1 visa. if F1 visa, additional evidence that parents are buying their own flight tickets