3.
What is the purpose of the method_missing method in Ruby?

4.
What is a singleton class in Ruby?

5.
What does the term "duck typing" refer to in Ruby?

7.
What is a closure in Ruby?

8.
What is memoization in Ruby?

9.
What is the purpose of the instance_eval method in Ruby?

10.
What does the term "monkey patching" refer to in Ruby?