Jesse Butterworth is the lead pastor of Rain City Church in Bellevue, Washington. He has 3 children. 2 of them are biologically his and 1 is adopted. Sometimes people ask incredibly rude questions about his adopted child, who is of a different race. Butterworth says, "Now we have to assume that people aren't meaning to actually be mean. They just don't know what kind of language to use when they're talking to an adoptive family."
So Butterworth offers this rule: treat adoption like breast augmentation. He says, "If you wouldn't say it about a boob job, don't say it about an adoptive family."
If you meet a woman whom you suspect has breast implants, you wouldn't say 'Hey, are those real?'or 'Where did you get those?'* Similarly, don't ask a parent 'Is that your real daughter?' or 'Where did you get her from?'
*Well, hopefully you wouldn't.
P.S. Be sure to read Miss Cellania's insightful comments on the topic.