Which of the following events occurred in the year 2001?

The September 11 Terrorist Attack is a significant event that occurred in 2001, marking a pivotal moment in both American history and global geopolitics. On September 11, terrorists affiliated with al-Qaeda hijacked four commercial airliners, using them as weapons to strike major U.S. landmarks, including the World Trade Center in New York City and the Pentagon in Arlington, Virginia. This event led to extensive loss of life and triggered widespread changes in U.S. foreign and domestic policies, including the initiation of the War on Terror and significant changes in national security measures.

In contrast, the other events listed occurred in different years. The Columbine High School Shooting took place in 1999, becoming one of the first major school shootings to receive extensive media coverage. Barack Obama was elected as president in 2008, becoming the first African American to hold the office. The emergence of China as a world leader is a process that has unfolded over several decades but gained particular prominence in global discussions in the 21st century, especially post-2001, as China's economy expanded rapidly and its influence on the global stage grew.