Which of the following is not a part of Amitav Ghosh’s Ibis trilogy?

The correct option/answer is: The Calcutta chromosome.

Explanation:
Amitav Ghosh’s acclaimed Ibis trilogy is a historical fiction series that set in the first half of the 19th century, dealing with the trade of opium between India and China under the British Raj. The three novels that comprise this trilogy are:
1. Sea of Poppies (2008)
2. River of Smoke (2011)
3. Flood of Fire (2015)

In contrast, The Calcutta Chromosome is a medical thriller and science fiction novel by Amitav Ghosh published in 1995. It deals with malaria research, secret societies, and reincarnation, making it completely separate from the theme, characters, and storyline of the Ibis trilogy.