The correct option is A Conquest of one country by an other state
The concept of state sovereignty entails that states are in comprehensive and exclusive control of all the people and property within their territory. State sovereignty also implies that all states are equal as states. As all states are on par with one another, one state cannot interfere with the internal affairs of another state. Essentially, sovereignty demands that one state cannot claim that another state takes any particular internal action. Hence, if the conquest of one country is done by another, the sovereignty of the former gets affected.