Step 1 :The question is asking for the country that occupies the 25th percentile in population. The 25th percentile is the value below which 25% of the data falls.
Step 2 :To find this, we need to sort the countries by population and find the country that is one quarter of the way through the list.
Step 3 :Since there are only 5 countries, the 25th percentile would be the country with the second smallest population.
Step 4 :Organizing the countries and their populations, we have: 'Country A' with 1374 million, 'Country B' with 333 million, 'Country C' with 139 million, 'Country D' with 36 million, and 'Country E' with 1281 million.
Step 5 :Sorting these by population, we get: 'Country D' with 36 million, 'Country C' with 139 million, 'Country B' with 333 million, 'Country E' with 1281 million, and 'Country A' with 1374 million.
Step 6 :The country that occupies the twenty-fifth percentile in population is the second one in this list.
Step 7 :Final Answer: The country that occupies the twenty-fifth percentile in population is \(\boxed{\text{Country C}}\).