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.
The rule of thumb When I started in photography the rule of thumb was really simple. When hand holding your camera the shutter speed should match or exceed the lens focal length. In other words if you wanted a sharp, shake free shot with a 50mm lens your shutter speed would be 1/50 th sec or faster. Whilst that was fine in its day the world has moved on and so has my rule.