Explanation
We can perform filter, URL and highlight actions out of the above given choices on a dashboard. Please refer to the image below:

Explanation
GDP / Population = GDP Per Capita

Here Sum is a function, / and + are operators. On the bottom there are comments.

Explanation
When users connect to Tableau, the data fields in their data set are automatically assigned a role and a type.
Role can be of the following two types:
1) Dimension
2) Measure
Type can be of the following :
1) String
2) Number
3) Geographic
4) Boolean
5) Date
6) Date and Time

Explanation
Tableau Data Extract (TDE) is a snapshot of the data that Tableau stores locally. Good for very large datasets of which we only need few fields. Performance is optimised because it queries its own database engine instead of the local data source.
When you create an extract of your data, you can reduce the total amount of data by using filters and configuring other limits. After you create an extract, you can refresh it with data from the original data. When refreshing the data, you have the option to either do a full refresh, which replaces all of the contents in the extract, or you can do an incremental refresh, which only adds rows that are new since the previous refresh.
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.

Explanation
Tableau Public is a free service that lets anyone publish interactive data visualizations to the web.
Visualizations that have been published to Tableau Public ("vizzes") can be embedded into web pages and blogs, they can be shared via social media or email, and they can be made available for download to other users.
Check it out : https://public.tableau.com/en-us/s/