Survivors are escorted from the National Bardo Museum in Tunis on Wednesday. At least 20 foreign tourists were killed in the attack. Mohamed Krit/Barcroft Media/Landov hide caption

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Yes, those are people: A still image from a drone video filmed inside the world's largest cave shows cavers standing beneath one of two large skylights in Vietnam's Hang Son Doong. Ryan Deboodt /Vimeo hide caption

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Jarvis Summers of the Mississippi Rebels sits on the court in the closing seconds of his team's 17-point comeback win against Brigham Young during the first round of the 2015 NCAA Men's Basketball Tournament. Joe Robbins/Getty Images hide caption

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Secret Service Director Joseph Clancy testifies before a Homeland Security Subcommittee hearing on the Secret Service budget Tuesday, when he responded to sharp questions about misconduct by his agents. Jim Lo Scalzo/EPA /LANDOV hide caption

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Bhutanese football player Chencho Gyeltshen controls the ball in a March 5 match against Sri Lanka. The striker hit two goals Tuesday to lead Bhutan past Sri Lanka and into the next phase of World Cup Qualifying. Lakruwan Wanniarachchi/AFP/Getty Images hide caption

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San Francisco 49ers linebacker Chris Borland (50) is seen here in a game last year against the New York Giants. Borland, who had two interceptions in that game, has announced that he is retiring from the NFL after his rookie season. Chris Szagola/CSM/Landov hide caption

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An Israeli woman votes with her daughter at a polling station in the coastal city of Haifa on Tuesday. Israel faces an unpredictable election to determine whether Prime Minister Benjamin Netanyahu will remain in power. Ahmad Gharabli /AFP/Getty Images hide caption

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A still image from surveillance video that was entered as evidence shows Boston Marathon bombing suspect Dzhokhar Tsarnaev in 2013, in a handout photo provided by the U.S. Attorney's Office in Boston. Tsarnaev, 21, is accused of killing three people and injuring 264 with a pair of homemade bombs at the race's crowded finish, as well as fatally shooting a police officer three days later. Handout Photo/Reuters /Landov hide caption

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Stefano Gabbana (left) and Domenico Dolce, seen here during the recent Milan Fashion Week, are being criticized for remarks about same-sex families, sparking a boycott led by musician Elton John. Daniel Dal Zennaro/EPA/Landov hide caption

itoggle caption Daniel Dal Zennaro/EPA/Landov