Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: DENVER, Colorado (CNN) -- Sen. Barack Obama laid out his plan for change in America as he accepted the Democratic presidential nomination Thursday night, securing his place in history as the first African-American to lead a major party ticket. Sen. Barack Obama accepted his party's nomination for the presidency Thursday night. "Change happens because the American people demand it -- because they rise up and insist on new ideas and new leadership, a new politics for a new time. America, this is one of those moments," he told supporters at the Democratic National Convention. "I believe that as hard as it will be, the change we need is coming."Barack Obama pits himself against John McCainObama lays out roadmap for improving the economyTens of thousands pile into Invesco Field to watch the speechAl Gore urges Americans to vote for change; vote for Obama 
 Question:He wrapped up his speech by telling the crowd, "_, we cannot turn back.

America