The State is a complex entity that consists of various elements. These elements work together to form the structure of a State.

Option 1: Population is an essential element of a State. It refers to the people who live within the geographical territory of a State and are subject to its authority. The population contributes to the overall character and functioning of the State.

Option 2: Land is also a crucial element of the State. It refers to the physical territory, including its natural resources and geographical boundaries. Land provides the space for the State to establish its sovereignty and exercise control.

Option 3: Alert - The correct answer should be "Sovereign." The State is characterized by its sovereignty, which means it has the ultimate and exclusive authority within its territory. The army is a tool of the State used to enforce its sovereignty and maintain control over its territory. Therefore, the army is indeed an element of the State.

Option 4: Government is an essential element of the State. It refers to the system or group of individuals that have the authority to make and enforce laws, manage public affairs, and administer public services. Government plays a crucial role in maintaining order and providing governance within the State.

In conclusion, the correct answer is option 3 - "Army."