what is the fourth largest country
Check this site for your answer.
http://worldatlas.com/aatlas/populations/ctyareal.htm
In area? In population? What?
http://www.infoplease.com/ce6/us/A0850088.html
http://en.wikipedia.org/wiki/List_of_countries_by_population
??
To determine the fourth largest country in the world by land area, you can refer to the website worldatlas.com, specifically the page on country sizes (http://worldatlas.com/aatlas/populations/ctyareal.htm). This website provides information on the land area of different countries.
If you are interested in the fourth most populous country, you can refer to websites like infoplease.com (http://www.infoplease.com/ce6/us/A0850088.html) or Wikipedia's list of countries by population (http://en.wikipedia.org/wiki/List_of_countries_by_population). These sources list countries according to their population size.
Please specify which type of ranking (area or population) you are looking for, and I can provide more specific information or guide you to the appropriate resource.