Explanation:

- The Government of National Capital Territory of Delhi (Amendment) Bill, 2021, amends an older legislation.

- This previous act is the Government of National Capital Territory of Delhi Act, 1991.

- This Act was originally enacted by the Parliament to enhance governance in Delhi by defining the powers of the elected government and the Lieutenant Governor.

- 1991: This is the correct year when the original Act was enacted.

- 1998, 1994, and 1996 are not associated with the enactment of this particular Act.

- Your Answer: Option 4 - 1991.

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