Ideally, a hydrogen fuel-cell vehicle has no environmental impact. Energy is produced by combining hydrogen with oxygen pulled from the atmosphere, and the tailpipe emission is water. The hydrogen fuel could come from a number of sources (Iceland recently started pulling it out of the ground).
A fast shutter speed such as 1/400th of a second will produce a series of crisp frames that have a choppy look when played back. A slow shutter speed such as 1/30th of a second, on the other hand, will produce a series of slightly blurred frames that have a smoother look when played back.
Increasing ISO to a higher number allows you to shoot at higher shutter speeds. In low-light conditions, even a slight increase in shutter speed can help to get a sharp photograph. There is a huge difference between 1/25th and 1/50th of a second shutter speed, while there is only one stop of ISO increase in between.