31.
What is the difference between a class method and an instance method in Ruby?

34.
What does the `protected` keyword do in Ruby classes?

35.
In Ruby, what is the purpose of the `super` keyword when used in a method?

37.
What is the purpose of the `extend` keyword in Ruby classes?

39.
What is the purpose of encapsulation in Ruby classes?

40.
What is the purpose of inheritance in Ruby?