An abandoned tank left by Boko Haram, February 20, 2016, seen on the road to Michika, Nigeria – a town formerly occupied by the insurgents. On April 14, 2014, 300 schoolgirls in the Chibok village in Nigeria were kidnapped by the terrorist group, Boko Haram. Two years later, the majority of these girls are still missing. According to the Global Terrorism Index Report 2015, Boko Haram, which operates mainly in Nigeria, has become the most deadly terrorist group in the world. (Photo by Danielle Villasana)

St Andrews University students skinny dip in the sea as May Day celebrations in St Andrews, Scotland on April 30, 2017. Hundreds of revellers ditched their clothes and bravely jumped into the bitterly cold North Sea. (Photo by Alamy Stock Photos)

Russia's Maria Sharapova carries the torch during the opening ceremony of the 2014 Winter Olympics in Sochi, Russia, Friday, February 7, 2014. (Photo by Matt Dunham/Associated Press)

A goat named “White On The Right” bleats as it is paraded with other goats prior to a race during the annual Easter goat racing event at the Mount Pleasant recreation ground in Tobago April 6, 2015. (Photo by Andrea De Silva/Reuters)

People spray water in the street ahead of “Songkran”, the annual Thai New Year water-throwing festival, in Kowloon City, Hong Kong, China, 09 April 2017. The pouring of water is a key element in the festival as it represents purification and the washing away of one's sins and bad luck for the year. The event also includes a “Miss Songkran” pageant where contestants are clothed in traditional Thai dress, and a winner is crowned. This year's “Songkran” will begin in Thailand on 13 April 2017. (Photo by Alex Hofford/EPA)

An Indian girl smiles under a water splash at a water park as the temperatures reached 38 degree Celsius in Calcutta, eastern India, 12 June 2016. The summer or pre-monsoon season lasts from March to July in eastern India with the highest day temperatures ranging from 38 to 45 degrees Celsius. (Photo by Piyal Adhikary/EPA)

Women wearing traditional dresses with pins of pictures of former North Korean leaders Kim Il Sung and Kim Jong Il welcome foreign reporters on a government organised visit to the Kim Jong Suk Pyongyang textile mill in Pyongyang, North Korea May 9, 2016. (Photo by Damir Sagolj/Reuters)

This photo provided by NASA shows a full moon rising behind the United Launch Alliance Atlas V rocket with NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft onboard at the Cape Canaveral Air Force Station Space Launch Complex 41, Sunday, November 17, 2013, Cape Canaveral, Florida. NASA's next Mars-bound spacecraft, the Mars Atmosphere and Volatile Evolution, or MAVEN, is the first spacecraft devoted to exploring and understanding the Martian upper atmosphere. (Photo by Bill Ingalls/AP Photo/NASA)