Explanation:

- The Constitution of India has different parts, each dealing with specific aspects of governance.

- Part 20 of the Constitution specifically deals with the amendment of the Constitution. This part includes Article 368, which outlines the procedure for amending the Constitution.

- Option 3: 20 is the correct answer.

- Option 1: 18 deals with "Emergency Provisions" which outlines the situation and processes related to emergencies in the country.

- Option 2: 13 addresses "Fundamental Rights," including the importance and the inability to make laws abridging them.

- Option 4: 10 relates to the "Citizenship" of people in India, procedures, and conditions.