Flowers are placed on a plate inscribed with the names of 9/11 victims at the National September 11 Memorial and Museum in New York, the United States, on Sept. 11, 2022. Sunday marked the 21st anniversary of the 9/11 attacks. (Photo by Michael Nagle/Xinhua)
U.S. President Joe Biden participates in a ceremony marking the 21st anniversary of the 9/11 attacks at the Pentagon in Arlington, Virginia, the United States, on Sept. 11, 2022. (Photo by Ting Shen/Xinhua)
People attend a commemoration ceremony of the 21st anniversary of the 9/11 attacks in New York, the United States, on Sept. 11, 2022. (Photo by Michael Nagle/Xinhua)