Officials from around the world have agreed to support a 1. ________ increase in hydrogen technology. Japan announced Wednesday that energy ministers or delegates from 30 countries are supporting a plan to develop hydrogen energy for 2. ________ . The 30 countries reportedly agreed to calls to increase production of hydrogen-powered mobility systems, such as fuel cell vehicles, trucks, buses, trains or ships. The goal is to make 3. ________ such systems available worldwide over the next 10 years. 4. ________ , Japan said the officials supported a goal of setting up 10,000 hydrogen refueling stations worldwide by 2030. Such stations will be necessary to lead a successful expansion of hydrogen-powered vehicles in coming years, a statement said. To date, Asian nations are a leader in developing hydrogen technology to power automobiles. China, Japan and South Korea have set 5. ________ to put millions of hydrogen-powered vehicles on roads by 2030. Experts have predicted the effort will cost the countries billions of dollars. Hydrogen is considered an 6. ________ clean energy source. Water and heat are the only byproducts of producing it. Also, hydrogen can be made from many different sources, including methane, coal, water, or even waste. Some critics of hydrogen fuel cell technology argue that hydrogen-powered vehicles will always be a very small part of the automobile market. But 7. ________ say that hydrogen is the cleanest energy source available for cars. They believe the technology will gain greater 8. ________ in the coming years, as more refueling equipment for hydrogen-powered vehicles is created and becomes more widely available. Many backers in China and Japan see hydrogen fuel cell vehicles as complementing electric automobiles instead of 9. ________ them. In general, hydrogen is considered a better choice for heavier vehicles that drive longer 10. ________ , like buses. So far, only a small number of automakers have made fuel cell passenger cars available to the public.