Part I: Fill in the blanks This is What's Trending Today. Sunday is September 11. It is the 15th anniversary of the day thousands of people were killed in a terrorist attack in the United States. Early that morning, two airplanes crashed into the towers of the World Trade Center in New York City. All the people on the planes were killed, along with thousands of people in the buildings. Another airplane crashed into the Pentagon building in Arlington, Virginia, outside of Washington, D.C. The Pentagon is the office of the U.S. Department of Defense. A fourth airplane crashed in a 1 part of Pennsylvania, when passengers fought back against terrorists who were planning to crash it into a Washington, D.C. landmark. On social media, people are 2 messages about their memories of that day, using the hashtags Never Forget and September 11. Ben Sturner lives in New York City. On Thursday, he posted a photo to Twitter showing the reflection of light off one of the new towers at the old : 3 of the World Trade Center. It was shared and liked thousands of times. States and cities around the U.S. are remembering people who died. Staten Island is a small part of New York City. It is an island in New York 4 , close to the Statue of Liberty and the location of the World Trade Center. Many people in that small community died. The local newspaper is remembering their lives by tweeting their photos one 5 . On Friday morning, many U.S. lawmakers gathered outside the Capital Building in Washington, D.C. to remember those who were killed. They 6 in a moment of silence and also sang "God Bless America." Some people will run almost 400 kilometers from the Pentagon to New York City to honor the firefighters, policemen and 7 workers who saved many lives that day. They started on Friday in Virginia and will finish on Sunday in New York City. But the anniversary of September 11, 2001, would not be complete without some businesses 8 sales. In the U.S., that is a big mistake. Many people used Twitter and Facebook to complain about a small mattress store in Texas that made a 9 related to September 11. The video 10 a woman standing in front of two stacks of twin-sized mattresses. The World Trade Center buildings were also called the Twin Towers. And that's What's Trending Today. I'm Dan Friedell.