What is the scope of a private instance variable? O All classes in the same package as the class in which the variable is defined. O Only the method in which the variable is defined. The entire class in which the variable is defined. The entire program.

Note: Question of Object-oriented programming

If the programmer doesn't declare any constructors for an extended class, what constructors will be inherited from the superclass? How does this inherited constructor initialize new instance variables that are not part of the superclass?   Suppose that Vehicle is a class and Car is a new class that extends Vehicle. Write a description of which kind of assignments are permitted between Car and Vehicle variables.   Suppose you write a new constructor for an extended class. Describe two different ways that the superclass's instance variables could be initialized within the constructor for the extended class.

Draw the following Class Structure as a (class digram):   1. NotificationSystem: This is the main class that manages the notification system. It has the following attributes and methods: - Attributes:   - users: a list of User objects representing all the users registered in the system   - tweets: a list of Tweet objects representing all the tweets posted in the system - Methods:   - register_user(user): adds a new user to the system   - post_tweet(user, message): posts a new tweet on behalf of a user   - get_timeline(user): returns a list of tweets from all users that the specified user follows   - get_mentions(user): returns a list of tweets that mention the specified user   2. User: This class represents a user in the system. It has the following attributes and methods: - Attributes:   - username: a string representing the username of the user   - followers: a list of User objects representing all users who follow this user   - following: a list of User objects representing all…