Name three causes of war and which is most convincing.

A war refers to an armed conflict between societies or countries. It can happen within a country in the form of civil war or between two or more countries. Civil war is also called domestic or internecine war. Recent examples of civil wars in the history of the world are the Libyan revolt (2011) and the Somali civil war that is still going on (since 1991). An example of a war between two countries is the Indo-Pakistani war of 1947.
Wars can be caused by:
Economic gain
Wars can be caused by the need for one country or region to control the wealth of another, hence making an economic gain. This is particularly common in developing countries that struggle with regional imbalances brought about by poor economic advancement policies of the central governments. An example in this case is the war in Sudan, where the Southerners were heavily marginalized yet owned significant oil resources.
Religion
Religious wars can happen between different religions or even different sects within a given religion. They are enhanced by other causes of war such as revenge or even nationalism. An example is the Lebanese civil war of 1975 that was caused by a struggle for government control between Shiite Muslims and the Sunnis.
Territorial gain
This happens when one country engages in armed conflict with others so as to amass land that it can call its own. An example is the territorial expansion of Germany during World War II.
Of the given causes of war, I find the first, economic gain, most convincing in modern day society. Since today countries have clearly defined boundaries, it is highly unlikely that a war can erupt out of the need of one country to aggressively acquire land belonging to another country. 
https://web.stanford.edu/~jacksonm/war-overview.pdf