Hi. I have a question about the third to last line of dialogue below - Which one of the two options is more natural? And would you say "Who'd" instead of "Who did" and "Who've" instead of "Who have" in the sentence?

A - You don't know what it's like, OK?

B - I don't?

A - No, you don't.

B - Do you think you're the only one who's experienced losing someone close?

A - Who did you lose?/Who have you lost?

B - My mom. She died when I was little.

A - I'm sorry. I didn't know.


The given third to the last line is okay as written - either of the two choices can be used. Here you wouldn't contract "Who did" or "Who have". This is an emphatic statement about a serious issue, and such statements are not contracted.