The book "Ayodhya: 6 December 1992" was authored by P.V. Narasimha Rao, making option 2 the correct answer.

To provide a bit of context for each option:

1) Chandra Shekhar was a politician who served as the 8th Prime Minister of India, but he did not write this book.

2) P.V. Narasimha Rao was the 9th Prime Minister of India and wrote the aforementioned book. The book delved into the events of that tumultuous day when the Babri Masjid was demolished in Ayodhya.

3) Jaswant Singh was an Indian Army officer and later a politician with the Bharatiya Janata Party, and he has written books on Indian history and politics, but not this particular one.

4) Arun Shourie is known as a journalist, author, and politician, and has written many books criticizing Indian government policies, but he didn`t write "Ayodhya: 6 December 1992".

Thus, the correct answer is option 2: P.V. Narasimha Rao.