Task: Question Answering
Input (English): passage: The Willis Tower, built as and still commonly referred to as the Sears Tower, is a 110-story, 1,450-foot (442.1 m) skyscraper in Chicago, Illinois. At completion in 1973, it surpassed the World Trade Center towers in New York to become the tallest building in the world, a title it held for nearly 25 years; it remained the tallest building in the Western Hemisphere until the completion of a new building at the rebuilt World Trade Center site in 2014. The building is considered a seminal achievement for its designer Fazlur Rahman Khan. The Willis Tower is the second-tallest building in the United States and the Western hemisphere -- and the 16th-tallest in the world. More than one million people visit its observation deck each year, making it one of Chicago's most-popular tourist destinations. The structure was renamed in 2009 by the Willis Group as part of its lease on a portion of the tower's space.
 question: was the sears tower ever the tallest building in the world?
Output (English): Yes