To answer this question, we need to understand the different modifiers that can be used in a Java interface.

In a Java interface, the following modifiers can be used:

A) final: This modifier indicates that the value of the variable cannot be changed once it is assigned. It is valid to use the final modifier in an interface variable declaration. Therefore, option A is valid.

B) native: This modifier is used to indicate that a method is implemented in a language other than Java. It is not valid to use the native modifier in an interface variable declaration.

C) abstract: This modifier is used to indicate that a method or class does not have an implementation and must be implemented by a subclass. It is not valid to use the abstract modifier in an interface variable declaration.

D) protected: This modifier is used to indicate that a variable, method, or class can only be accessed within its own package or by a subclass of its class. It is not valid to use the protected modifier in an interface variable declaration.

Therefore, the three valid modifiers to use on line 12 are final.

• Thanks
• Wrong explanation

To answer this question, let's go through each option:

Option A) final - This option is valid on line 12. The "final" keyword is used to indicate that a variable's value cannot be changed once it has been assigned a value. In this case, the variable "MY_VALUE" is assigned the value 10, and since it is declared as "final", its value cannot be changed.

Option B) native - This option is not valid on line 12. The "native" keyword is used in the declaration of a method to indicate that the method's implementation will be provided by a native code, typically written in a language like C or C++. It is not applicable to variables.

Option C) abstract - This option is not valid on line 12. The "abstract" keyword is used to indicate that a class or method does not have an implementation and must be overridden by a subclass. It is not applicable to variables.

Option D) protected - This option is not valid on line 12. The "protected" keyword is used to specify that a member (variable or method) can only be accessed within its own package or by a subclass of its class. It is not applicable to variables.

Therefore, the three valid options on line 12 are A) final, C) and F) abstract.

• Thanks
• Wrong explanation

To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) Foo f = (Delta)x; - This option is incorrect because it is casting the object 'x' of type Beta to type Delta. Since Beta is a subclass of Delta, this cast is valid and will not throw a ClassCastException.

Option B) Alpha a = x; - This option is incorrect because it is assigning the object 'x' of type Beta to a reference variable 'a' of type Alpha. Since Beta is a subclass of Alpha, this assignment is valid and will not throw a ClassCastException.

Option C) The code on line 31 throws an exception. - This option is incorrect because line 31 is not present in the given code.

Option D) Foo f = (Alpha)x; - This option is incorrect because it is casting the object 'x' of type Beta to type Alpha. Since Beta is a subclass of Alpha, this cast is valid and will not throw a ClassCastException.

Option E) Beta b = (Beta)(Alpha)x; - This option is incorrect because it is casting the object 'x' of type Beta to type Beta. Since Beta is already of type Beta, this cast is unnecessary and will not throw a ClassCastException.

The correct answer is A) Foo f = (Delta)x;. This option is incorrect because it is casting the object 'x' of type Beta to type Delta. Since Beta is not a subclass of Delta, this cast is invalid and will throw a ClassCastException.

• Thanks
• Wrong explanation