1. How are UNUserNotificationCenter and NotificationCenter different?

a) One is responsible for showing notifications to users, and the other is a mechanism to send notifications about events inside an app.

2. What kinds of notifications can you send to a user?

a) Push notifications and local notifications.

3. What are provisional notifications?

c) Notifications that are delivered to the user quietly, so they can preview the notifications your app will send.

4. How does iOS group notifications?

a) It uses the thread identifier from the notification content and the app that the notification belongs to.

5. What does a notification service extension do?

c) It allows you to replace a notification's contents before the user sees it.

6. What does a notification content extension do?

b) It allows you to create a custom interface for when a user 3D-touches a notification.