Correct. Compared to the other options, option C is least likely to constitute a COI.
Re. A Receiving consulting fees, donations, gifts, honoraria or any form of personal payment from the manufacturer of an investigational product would be regarded as a financial COI.
Re. B Close personal relationships with those who have financial interests in your study could lead to a conflict of interests / obligations (duties as a spouse vs. duties as a researcher).
Re. C It is unlikely that you would need to declare this as a COI unless you think that it has affected or will affect your objectivity in conducting your study.