The correct answer is (d). The Fourth Ministerial Conference of the World Trade Organization (WTO) was held in Doha, Qatar from 9 to 14 November 2001.
The other options are incorrect.
(a) Singapore: The First Ministerial Conference of the WTO was held in Singapore from 9 to 13 December 1996.
(b) Geneva: The Second Ministerial Conference of the WTO was held in Geneva, Switzerland from 13 to 18 May 1998.
(c) Seattle: The Third Ministerial Conference of the WTO was held in Seattle, Washington, United States from 30 November to 3 December 1999.