United Nations Climate Action Summit 2019 was held at which of the following cities /

Correct: D (New York). The UN Climate Action Summit was convened by Secretary-General Antonio Guterres at UN Headquarters in New York on 23 September 2019. He asked heads of state to bring concrete, implementable plans to cut emissions, not just pledges.

Why the others are wrong:

• Paris: Paris hosted COP21 in 2015, which produced the Paris Agreement. That was a UNFCCC conference, not this 2019 summit.
• Geneva: Geneva is a major UN hub (WHO, WMO, UNHCR), but this summit was not held there.
• Doha: Doha hosted COP18 in 2012, which adopted the Doha Amendment to the Kyoto Protocol. It has no link to the 2019 summit.

Core concept: Distinguish the UN Secretary-General's climate summit from the annual UNFCCC Conference of Parties (COP). Summits are convened by the SG to build political momentum; COPs are treaty-body negotiations. This matters for Mains questions on climate governance and India's position in multilateral forums.

Trap: Aspirants often pick Paris because of COP21, or Madrid (COP25, December 2019), and assume every climate meeting of 2019 was a COP.