[单项选择]Helium is not flammable and, next to hydrogen, is ...... (a)known the lightest gas (b)lightest the known gas (c)the lightest gas known (d)the known gas lightest

[填空题]We must derive hydrogen from renewable sources with a view to a pure hydrogen economy.

[填空题]Possible sources for the hydrogen are both electrolysis of water and______.

[填空题]The bacteria depend on worms for hydrogen sulfide in the symbiotic relationship.

[单项选择]Hydrogen is the fundamental element of the universe （　） it provides the building blocks from which the other elements are produced.
A. so that
B. but that
C. in that
D. provided that

[填空题]The development of the hydrogen station network would be greatly affected by the process of __________________ of storage technology.

[填空题]Concerning the future of the hydrogen economy, the most obvious step we will take is ____________.

[单项选择] THE HYDROGEN ECONOMY It seems like every day there is a new announcement in the news about automobiles powered by fuel cells. The promises are great, since fuel cells have the potential to very quickly double the efficiency of cars while significantly reducing air pollution. At the same time, there have been news stories for decades about the problems associated With petroleum. Everything from oil spills to ozone(臭氧) alerts to global warming gets blamed on our dependence on fossil(化石) fuels. These two forces are leading the world toward what is broadly known as the hydrogen economy. If the predictions are true, over the next several decades we will all begin to see an amazing shift away from the fossil fuel economy we have today toward a much cleaner hydrogen future. Problems with the fossil fuel economy While fossil fuels have played an important role in getting society to the point it is at today, there are four big problems that fossil
A. Y
B. N
C. NG