Explanation:

• The 42nd Amendment Act—sometimes called the "Mini-Constitution"—was passed during the Emergency in 1976.

• This was when Indira Gandhi was Prime Minister. She used this amendment to give more power to the central government and reduce the power of the judiciary.

• Option 1, Morarji Desai, came to power only after the Emergency, in 1977.

• Option 2, Rajiv Gandhi, is Indira’s son—he became Prime Minister later, after 1984.

• Option 4, Charan Singh, was Prime Minister just for about half a year in 1979-80, long after the 42nd Amendment.

So, the right answer is:

Option 3: Indira Gandhi