A participant competes in the “Nostalgic Ski Race” in the western town of Neuastenberg February 8, 2015. The “Nostalgic Ski Race” is held every two years with about 40 participants and is organized by the ski club of Neuastenberg, a town which was founded in 1713. The conditions for the participation in the race are vintage skis and dresses. (Photo by Ina Fassbender/Reuters)

People ride a prototype of a driverless vehicle as it is moves through a pedestrian area in Greenwich, east London, February 11, 2015. Britain has begun testing driverless cars in four cities, launching the first official trials ahead of a series of planned rule reviews to accommodate the new technology. (Photo by Suzanne Plunkett/Reuters)

Model Helen Kwok displays the nail art completed by a competitor at the Canada Nail Cup in Vancouver, Monday, February 16, 2015. Nail artists competed in multiple categories at the event, which according to organizers is the only nail competition in the country. (Photo by Darryl Dyck/AP Photo/The Canadian Press)

Bangladeshi relatives wail near bodies of victims after a river ferry carrying about 100 passengers capsized Sunday after being hit by a cargo vessel,in Manikganj district, about 40 kilometers (25 miles) northwest of Dhaka, Bangladesh, Sunday, February 22, 2015. (Photo by A. M. Ahad/AP Photo)

A villager watches as Mount Sinabung volcano erupts, in Kuta Tengah village, Karo Regency in Indonesia's North Sumatra April 1, 2015. The Indonesian volcano was dormant for 400 years before erupting in 2010. (Photo by Y. T. Haryono/Reuters)

In this Wednesday, March 18, 2015 photo, limestone quarry workers walk through a cloud of dust spewed into the air by rotor blades of the stone-cutting machinery in the desert of Minya, southern Egypt. Around 45,000 people, including children, work in an estimated 1,500 quarries, digging out stones that later will be used in construction or powdered to be used by pharmaceutical and ceramic companies. (Photo by Mosa'ab Elshamy/AP Photo)

People carry cutouts of coffins during a march to commemorate the more than 617 people they say have been killed by law enforcement in LA County since 2000, in Los Angeles, California April 7, 2015. (Photo by Lucy Nicholson/Reuters)