Indian Air Force officers stretch before taking part in full dress rehearsal for India's Republic Day parade in Kolkata, January 23, 2018. (Photo by Rupak De Chowdhuri/Reuters)

A Hawaiian cleaner wrasse provides its cleaning services to a yellowfin goatfish in a reef community off the Big Island in Hawaii. Cleaner species help rid their hosts of ectoparasites, dead tissue, bacteria and fungi. Studies have shown cleaning to play a vital role in keeping many reef ecosystems healthy. (Photo by Marty Snyderman/Caters News Agency)

Revellers take a break during the Carnival 2016 parade in Port-au-Prince, Haiti, February 8, 2016. (Photo by Andres Martinez Casares/Reuters)

A migrant labourer brushes his teeth in front of a scrapped helicopter model in Mumbai, India, April 13, 2016. (Photo by Danish Siddiqui/Reuters)

Recording artist Beyonce performs onstage during The 59th GRAMMY Awards at STAPLES Center on February 12, 2017 in Los Angeles, California. (Photo by Kevin Winter/Getty Images for NARAS)

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 sewer cleaner of Dhaka City Corporation cleaning out the city's sewers on May 03, 2017 in Dhaka, Bangladesh. Despite a rise in the number of deaths of manhole workers every year, workers regularly go into the manholes without any protective gear. (Photo by Zakir Chowdhury/Barcroft Images)

An Afghan man rides on his donkey, holding balloons for sale during Newroz Day celebrations, a festival marking their spring and new year, in Kabul, Afghanistan March 21, 2017. (Photo by Omar Sobhani/Reuters)