Ahydrogen-powered car creates no pollution when the car is driven; however, using this alternative fuel poses many challenges. which of the following choices is not one of them?

A hydrogen-powered car creates no pollution when the car is driven; however, using this alternative fuel poses many challenges. Which of the following is not one of them? 
a)The combustion of hydrogen is too violent to be useful to the public.  -- THIS IS THE ANSWER
b)Hydrogen is highly reactive. 
c)New fueling stations that can handle hydrogen would have to be built. 
d)Hydrogen gas is not naturally available in large quantities.

The answer is (A) because the fuel cells control the reaction of hydrogen. 

Organisms are more likely to be more preserved in mud than sand because mud is moist and wet, while sand is very dry.