The following is excerpted from US Embassy in China.
http://www.usembassy-china.org.cn/visa/c/faq.html
我告诉签证官我父母在中国,我肯定会回来。 我是独生子, 我会回来照顾双亲时, 签证官仍认为我的回国理由不充分, 为什么?
http://www.usembassy-china.org.cn/visa/faq.html
I will certainly return to China because my parents are here. I am the only son in my family and I need to return so that I can take care of my parents. Why did the officer say I have insufficient ties to compel me to return?