Among the options provided, the most likely attribute of an object is "a variable holding its weight."
Attributes of an object typically refer to the properties or data that describe the object, which are often represented as variables within the object's class. In this case, a variable that holds the object's weight would be a direct characteristic of that object.
The other options refer more to relationships (parent and child classes) or behavior (function), rather than to the object's intrinsic attributes.