Which statement about methods in relation to classes is true?

The chosen statement is accurate because methods are indeed designed to operate on the properties defined in a class. In object-oriented programming, methods serve as functions that belong to a class and can manipulate the data encapsulated within that class. When a method is invoked on an instance of a class, it often accesses or modifies the instance's properties, thereby providing functionality that is specific to that class.

For instance, consider a class representing a vehicle with properties like speed and fuel. A method within this class, such as accelerate(), would operate on the speed property to increase its value, thus demonstrating how methods interact directly with the attributes of the class.

The other options present misunderstandings about methods: the assertion that methods are exclusive to instances disregards the presence of static methods, which can be called without an object instance. Claiming that methods cannot be defined in a class is misleading, as methods are fundamental components of a class in object-oriented programming. Lastly, it's not true that methods must return a value; methods can be defined to return a value or to be Unit (similar to void in other languages), meaning they perform an action without returning anything.