Aerial photo taken on April 20, 2018 shows the view of advection fog above Qingdao, a coastal city in east China' s Shandong Province. (Photo by Lu Hui/Xinhua News Agency/Eyevine)

Children wearing military uniform take part in a parade, held by Russian servicemen, pupils of infant and primary schools, which is a public event to honour World War Two veterans and to mark the upcoming Victory Day, in Rostov-on-Don, Russia on April 25, 2019. (Photo by Sergey Pivovarov/Reuters)

Indian Students of Rabindra Bharati University at the BT Road Campuses Celebrates the Holi, Color Festival on March 09, 2017 in Kolkata.Holi, the popular Hindu spring festival of colours is observed in India at the end of the winter season on the last full moon of the lunar month, and will be celebrated on March 13 this year. (Photo by Debajyoti Chakraborty/NurPhoto)

A girl collects water lily flowers at a pond in Kampong Speu province Cambodia, March 24, 2017. Picture taken March 24, 2017. (Photo by Samrang Pring/Reuters)

Vishnu Limbachiya, a hair artist, styles the hair of a man while wearing a blindfold at a park in Ahmedabad, India, May 31, 2017. (Photo by Amit Dave/Reuters)

Syrian Internal Security Forces dance in celebration during their graduation ceremony, at Ain Issa desert base, in Raqqa province, northeast Syria, Thursday, July 20, 2017. Some 250 residents of Syria's Raqqa province are the latest batch to graduate from a brief U.S-training course that is preparing an internal security force to hold and secure areas as they are captured from Islamic State militants. (Photo by Hussein Malla/AP Photo)

A man is silhouetted in front of the Allianz-Arena as he walks his dogs at sunrise in Munich, southern Germany, Friday, April 10, 2015. (Photo by Peter Kneffel/AP Photo/DPA)

Pro-Russian rebels stand near a monument during a ceremony to honour the World War Two defenders of Donetsk from Nazi forces, in Donetsk, in this September 8, 2014 file photo. (Photo by Marko Djurica/Reuters)