(FILES) International Atomic Energy Agency (IAEA) chief Rafael Grossi talks to the press on a road outside Zaporizhzhia city, after his visit to the Russian-held Zaporizhzhia nuclear power plant in southern Ukraine on September 1, 2022, amid the Russian invasion of Ukraine. Four contenders are squaring up to succeed Antonio Guterres as leader of the United Nations, which faces unprecedented global instability, wars and its own crushing budget crisis. Chile's Michelle Bachelet, Argentina's Rafael Grossi, Costa Rican Rebeca Grynspan, and Senegal's Macky Sall will each face grillings by 193 member states and NGOs for three hours on April 21 and April 22. It is only the second time the UN has held a public Q&A, a format created in 2016 to boost transparency. (Photo by Genya SAVILOV / AFP via Getty Images)