Explanation:

Single constitution: India has a single Constitution for the entire nation, including the states. This is a unitary feature as most federal nations have separate constitutions for their constituent units.

Emergency Provisions: The provisions related to the emergency, when invoked, empower the central government to exercise full control over the state machinery, overriding the federal structure.

All-India Services: Services like IAS, IPS, and IFS are under the control of the central government, but they work in the states. This creates a bridge between the center and the states and ensures that the center has a say in the state's administration.

Integrated Election Machinery: The Election Commission of India conducts elections for both the center and the states. This is a unitary feature.

Appointment of Governor: The Governor, who is the ceremonial head of a state, is appointed by the President of India on the advice of the central government. The role and powers of the Governor, especially in contentious situations, tend to favor the center over the states.

Given the above explanations, all the mentioned features (1, 2, 3, 4, and 5) are unitary in nature.

Thus, the correct answer is:

4. 1, 2, 3, 4, and 5.