To answer this question, let's go through each option to understand why it is correct or incorrect:
Option A) Foo.beta() is a valid invocation of beta() - This option is incorrect because the beta() method is an instance method and cannot be invoked using the class name. It should be invoked on an instance of the Foo class.
Option B) Foo.alpha() is a valid invocation of alpha() - This option is correct. The alpha() method is a static method, and static methods can be invoked using the class name.
Option C) Method beta() can directly call method alpha() - This option is correct. Since both beta() and alpha() are methods of the same class, the beta() method can directly call the alpha() method without any issues.
Option D) Method alpha() can directly call method beta() - This option is incorrect. The alpha() method is a static method, while the beta() method is an instance method. Static methods cannot directly call instance methods without creating an instance of the class.
The correct answers are B and C.