In what way can abstract classes differ from interfaces?

Abstract classes can indeed contain both abstract methods (which do not have an implementation) and concrete methods (which do have an implementation). This capability allows abstract classes to provide some shared functionality that can be inherited by subclasses, offering a mix of abstract behavior that must be implemented and concrete behavior that can be reused.

On the other hand, interfaces, particularly in versions of Java prior to Java 8, could only contain abstract methods. However, from Java 8 onward, interfaces can include default methods with an implementation, but the primary purpose of interfaces is still to define contracts with abstract methods, ensuring that implementing classes provide their own behavior.

This distinction allows abstract classes to serve as a common base with some implemented features, whereas interfaces focus primarily on the unification of disparate classes without providing inherent behavior. Therefore, the option about abstract classes being able to contain concrete methods while interfaces cannot is accurate.