Stat A)  An abstract class is a class which contains some abstract methods as well as concrete methods also. Stat B)  Consider that class that contains only abstract methods, and there are no concrete methods. It becomes an abstract class. Stat C) This means an interface is an abstract class but it contains only abstract methods. None of the methods in interface can be defined.  Stat D) Only method names or headers can be written in interface. So that an interface can be defined as a specification of method headers.ABCD TrueACD TrueBCD TrueAD True

Stat A) True - An abstract class can indeed contain both abstract and concrete methods.

Stat B) True - A class with only abstract methods can be considered an abstract class.

Stat C) True - An interface is a type of abstract class that only contains abstract methods.

Stat D) True - An interface can only contain method headers, not their definitions.

Stat A) True - An abstract class in object-oriented programming is indeed a class that can contain both abstract (undefined) and concrete (defined) methods.

Stat B) True - A class with only abstract methods can be considered an abstract class. However, it's important to note that this is not a requirement for a class to be abstract; it can contain concrete methods as well.

Stat C) True - An interface is similar to an abstract class in that it can only contain abstract methods. However, an interface is not technically an abstract class. It's a separate concept in object-oriented programming.

Stat D) True - In an interface, only method signatures (names and parameters) are provided. The methods are not defined (they don't have a body) in the interface itself. They must be defined by any class that implements the interface.

So, all the statements A, B, C, and D are true.

Stat A) True - An abstract class can indeed contain both abstract and concrete methods.

Stat B) True - A class with only abstract methods can be considered an abstract class, but it's more commonly referred to as an interface in languages like Java.

Stat C) True - An interface is a type of abstract class that only contains abstract methods. In some languages like Java, none of the methods in an interface can have a body (be defined).

Stat D) True - In an interface, only method signatures (names or headers) can be declared. The methods are defined in the classes that implement the interface. So, an interface can indeed be seen as a specification of method headers.

So, all the statements ABCD, ACD, BCD, and AD are true.

Stat A) True - An abstract class can indeed contain both abstract and concrete methods.

Stat B) True - A class with only abstract methods can be considered an abstract class.

Stat C) True - An interface is similar to an abstract class in that it can only contain abstract methods.

Stat D) True - An interface can only contain method headers, it cannot define the implementation of the methods.

Stat A) True - An abstract class can indeed contain both abstract and concrete methods.

Stat B) True - A class with only abstract methods can be considered an abstract class.

Stat C) True - An interface is a type of abstract class that only contains abstract methods.

Stat D) True - An interface can only contain method headers, not their definitions.

Stat A) True - An abstract class can indeed contain both abstract and concrete methods.

Stat B) True - A class with only abstract methods can be considered an abstract class.

Stat C) True - An interface is a type of abstract class that only contains abstract methods. However, it's important to note that while all interfaces are abstract classes, not all abstract classes are interfaces.

Stat D) True - Interfaces only contain method signatures (names or headers), not their implementations. They essentially provide a form of contract that implementing classes must follow.

Stat A) True - An abstract class can indeed contain both abstract and concrete methods.

Stat B) True - A class with only abstract methods can be considered an abstract class.

Stat C) True - An interface is a type of abstract class that only contains abstract methods.

Stat D) True - An interface can only contain method headers, not their implementations.