U.S. Department of Homeland Security Secretary Kirstjen Nielsen speaks during a visit to U.S. President Donald Trump's border wall in the El Centro Sector in Calexico, California, U.S. October 26, 2018. REUTERS/Earnie Grafton TPX IMAGES OF THE DAY© REUTERS/Earnie Grafton U.S. Department of Homeland Security Secretary Kirstjen Nielsen speaks during a visit to U.S. President Donald Trump’s border wall in the El Centro Sector in Calexico, California, U.S. October 26, 2018. REUTERS/Earnie Grafton TPX IMAGES OF THE DAYHomeland Security Secretary Kirstjen Nielsen said “everything is on the table” with regard to border security during the unveiling of a border wall project in California on Friday.Nielsen’s remarks came as the Trump administration considers ways to slow immigration at the U.S.-Mexico border and as a caravan of migrants — mostly made up of thousands fleeing violence and poverty in Central America — are making their way north through Mexico.