Answer:
"Su primas son de Chile."
Step-by-step explanation:
The correct sentence is "Su primas son de Chile." This sentence uses the correct forms of the possessive adjective "su" (his/her) and the plural noun "primas" (cousins) to indicate that the speaker's cousins are from Chile. The other sentences contain errors in the use of possessive adjectives and/or nouns, so they are not correct.