Final answer:
The correct answer is 'next of kin', meaning the closest living relative to a person. The speaker, being the only surviving daughter, is the heir to her father's estate.
Step-by-step explanation:
The correct answer to fill in the blank is option A) kin. In the context of the sentence, 'next of kin' refers to the closest living relative or relatives to a person. Therefore, as the only surviving daughter, the speaker would be considered the next of kin and be the heir to her father's wealth. The concept of kinship is important here, as it implies a biological or legally recognized relationship, although kinship can extend to those who are not biologically related but are legally or culturally recognized as family.