Explanation:

- Republic:

- A republic is a form of government where the country is considered a public matter.

- There is no monarchy; the head of state is usually an elected or nominated president.

- India is declared as a sovereign, socialist, secular, and democratic republic in its Preamble.

- Oligarchy:

- An oligarchy is a power structure where a small group of people have control over a country.

- This form of government is not applicable to India.

- Monarchy:

- A monarchy is a system where a state is ruled by a king, queen, or emperor.

- India does not follow a monarchy, as it abolished the princely states in 1950.

- Aristocracy:

- An aristocracy is a form of government in which power is held by the nobility.

- This was not adopted by India post-independence.