Detailed Instructions: 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].
Problem:Washington (CNN) -- President Barack Obama used a Memorial Day ceremony to say it is time for America to properly welcome home Vietnam veterans and show them and their families the respect and gratitude they deserved but didn't receive decades ago. "You came home and sometimes were denigrated when you should have been celebrated," Obama said beneath a scorching sun at the Vietnam Veterans Memorial. "It was a national shame, a disgrace that should have never happened. That's why here today, we resolve that it will not happen again." The event, which launched a 13-year Vietnam War 50th anniversary commemoration, was the culmination of a day of somber events on the annual holiday honoring America's war dead.NEW: President Obama calls the denigration of Vietnam veterans a "national shame""America will be there for you," Obama tells veterans and their familiesMemorial Day launches a 13-year commemoration of the Vietnam War's 50th anniversaryObama lays a wreath to the fallen at Arlington National Cemetery 
 Question:This year marks the 50th anniversary of the _ deploying a significant military presence in Vietnam.
Solution:
America