On May 2, 2012, Ashok Gadgil became the winner of the $100,000 Lemelson-MIT Award for Global Innovation  . Each year, the honor is given to an inventor who has made a big difference in the lives of people in developing countries. Gadgil is a professor and physicist at the University of California, Berkeley. He spent thirty years helping people in need. His inventions have helped more than 100 million people around the world. "I chose to focus on problems where my knowledge of science  could help," Gadgil said. In the 1990s, Gadgil designed his first life-saving invention after more than 10,000 people died from Bengal cholera   because of the clean water crisis   in India. His invention uses ultraviolet light to kill deadly disease-carrying germs   from drinking water. It costs just one cent to clean five liters of water (about 21 cups). So far, the invention has provided safe drinking water for more than five million people in India and other developing countries. Gadgil's another important invention is the Berkeley-Darfur Stove  . The long and violent war in Darfur, Sudan, has caused many people to move to foreign countries and live in refugee camps  . They are given food aid. But people still have to travel a long distance five times a week to gather firewood to cook meals. This can be dangerous because of street violence in the area. To avoid danger, some spend much of their money used to feed their families buying firewood. The stove Gadgil created cuts fuel usage by 55%. That means people wouldn't have to leave the camps to find firewood as often. The invention also helps to save homes more than $300 a year. About 125,000 people and their families have been helped. As a professor, Gadgil encourages his students, "Be optimistic   when you try a hard problem," he says. "It's when you solve a large problem that you can have a big influence on the world." Ashok Gadgil was given the honor because   _  .
he was a famous professor and physicist at UC, Berkeley he improved the lives of people in developing countries he spent thirty years helping people in need he developed useful inventions with his team