Explanation
Extracts are advantageous for several reasons:
1) Supports large data sets: You can create extracts that contain billions of rows of data.
2) Fast to create: If you're working with large data sets, creating and working with extracts can be faster than working with the original data.
3) Help improve performance: When you interact with views that use extract data sources, you generally experience better performance than when interacting with views based on connections to the original data.
4) Support additional functionality: Extracts allow you to take advantage of Tableau functionality that's not available or supported by the original data, such as the ability to compute Count Distinct.
5) Provide offline access to your data: Extracts allow you to save and work with the data locally when the original data is not available. For example, when you are traveling.
To work with the MOST up-do-date data, use a live connection instead!

Explanation
According to the official Tableau documentation:

Explanation
To reach the correct answer, follow these steps:
1) You can simply drag Country to the view, and look at the marks in the bottom left of Tableau Desktop - 147 marks!

2) Or, you can simply go to Data Source -> Country Tab -> Describe


As you can see, 147 members exist in this Country column!

Explanation
Exporting the visualisation gives us a static view of the visualisation.
It is NOT possible to interact with it, use filters, or dynamically enter anything in a visualisation exported PDF.
In Tableau Desktop, you can save views as PDF files rather than printing them as hard copies. You do not need to have Adobe Acrobat installed on your computer.
When you print an individual sheet to PDF, filters in the view are not included. To show filters, create a dashboard containing the sheet and export the dashboard to PDF. (IMPORTANT)

Explanation
The following options are available when an image is Exported:

NOTE: When we Copy an image rather than exporting it, then the image is copied to the clipboard in the TIFF file format! However, it is not available when EXPORTING an image.