4. Fill in the blanks with the appropriate design pattern for the given descriptions:

(a) The _____________________________ design pattern defines a family of algorithms, encapsulates each one, and makes them interchangeable.

(b) The _____________________________ design pattern treats individual objects and whole-part hierarchies of objects uniformly.

(c) The _____________________________ design pattern ensures that a class has only one instance, and provides a global point of access to it.

(d) The _____________________________ design pattern allows the requester of a particular action to be decoupled from the object that performs the action.

(e) The _____________________________ design pattern defines the skeleton of an algorithm in an operation, and defers some steps to client subclasses.