In these examples we select only some countries to print. A process that takes a list and selects only certain items is a "filter". Some get through, some don't.
You may need to review PHP:Testing_strings_and_numbers before you attempt these questions.
Selecting a region.
Print the countries where the region is Europe.
Picking the stans.
Countries with a z.
Small countries (by area).
Print the countries that have an area of less than 100.