Public Interest Litigation (PIL) was introduced to the Indian Judicial System under the term of Justice P. N. Bhagwati, who was the Chief Justice of India from 1985 to 1986, thus making option 4 the correct answer.

Option 1, Justice M. Hidayatullah, served as the Chief Justice of India from 1968 to 1970, before PIL was introduced. Similarly, option 2 and option 3, Justices A. M. Ahmadi and A. S. Anand, served from 1997 to 1998 and 1998 to 2001 respectively, roles which commenced after the initiation of PIL.

Hence, P. N. Bhagwati is the correct choice as he was the Chief Justice at the time PIL was introduced in India, thus expanding access to justice to a wider population.