The lights from this year’s Tribute in Light shone in the sky on Sept 11 in New York City, US. This art show helps people remember the 9/11 attacks. On Sept 11, 2001, 19 al-Qaeda terrorists (基地组织恐怖分子) hijacked (劫持) four planes. Two of the planes crashed (撞击) into the Twin Towers in New York City. The Twin Towers fell and nearly 3,000 people died.