The phrase "belonging to what person" can be expressed using a variety of synonymic phrases, each with its own nuances and contexts. For example, "property of" is a common term used to indicate ownership, as is "possession of." Additionally, "belonging to" itself can be modified with various personal pronouns to more specifically denote the owner, such as "his," "her," "their," or "its" depending on the subject in question. Other related phrases include "appertaining to," "pertaining to," and "associated with." Ultimately, the choice of synonym will depend on the specific context and desired tone or emphasis of the sentence.