Concept:The possessive form of a compound noun like "father-in-law" is formed by adding ’s to the last word: father-in-law’s.Explanation:The subject is "her", which refers to one father-in-law.So we need the singular possessive form."Father-in-law" takes the plural as "fathers-in-law", but its singular possessive is "father-in-law’s".Therefore, the correct phrase is "her father-in-law’s house."Answer:D. father-in-law's