Tree maps size begins from maximum in top left to smallest in bottom right.

See below to learn how to create a TreeMap and add colours to it:

Explanation
When you connect to a data source, Tableau automatically separates date fields into hierarchies so you can easily break down the viz. You can also create your own custom hierarchies. For example, if you have a set of fields named Region, State, and County, you can create a hierarchy from these fields so that you can quickly drill down between levels in the viz.

This is one of the most common questions on the Tableau Desktop Specialist Exam.
Wrong options -
1) Don't use backgrounds - This is not a solution. What if we want to use backgrounds? We can't just stop using backgrounds to solve this problem.
2) Decrease the font size - Do you think using a smaller font will make the text more readable? No right?
Hence, this is wrong too.
All other options are ways recommended to make your text more readable!

A bullet graph is a variation of a bar graph developed to replace dashboard gauges and meters. A bullet graph is useful for comparing the performance of a primary measure to one or more other measures. Below is a single bullet graph showing how actual sales compared to estimated sales.

The INNER JOIN keyword selects all rows from both tables as long as there is a match between the columns.
Consider 2 tables "Orders" and "Customers".
If there are records in the "Orders" table that do not have matches in "Customers", these orders will not be shown!