41.
What does the term "memoization" refer to in Ruby?

42.
What is the purpose of the Enumerator class in Ruby?

43.
What does the term "immutability" refer to in Ruby?

44.
What is the purpose of the String#<< method in Ruby?

45.
What does the "bang" (!) operator do when appended to a method name in Ruby?

46.
What is the purpose of the catch and throw keywords in Ruby?

48.
What is a "predicate method" in Ruby?

49.
In Ruby, what is the purpose of the __send__ method?

50.
What does the autoload method in Ruby do?