Which of the following is the characteristic of the Indian Constitution?

Presidential form of Government / अध्यक्षात्मक शासन
Incorrect.
India follows a Parliamentary form of Government, modeled on the British system, not the Presidential system like the USA.
Rigid as well as flexible / कठोर भी और लचीला भी
Correct.
The Indian Constitution is unique because some provisions can be amended easily (flexible), while others require a special majority and ratification by states (rigid).
Example:
Flexible: Changing the names of states.
Rigid: Amending Fundamental Rights requires a special majority.
Smallest constitution / सबसे छोटा संविधान
Incorrect.
India has the longest written constitution in the world, not the smallest.
Multiple citizenship / बहु नागरिकता
Incorrect.
India provides single citizenship to all its citizens, unlike countries such as the USA where both state and federal citizenship exist.
Significance
The blend of rigidity and flexibility ensures that the Constitution can adapt to changing needs while preserving its core principles.
This balance has helped India maintain stability and continuity in governance for over seven decades.
In short: The Indian Constitution is characterized by being rigid as well as flexible, allowing both stability and adaptability.