Like the millipedes, centipedes are highly segmented (15 to 177 segments), but with only one pair of walking legs per segment (millipedes have two legs per segment). The head of a centipede has a pair of antennae, jaw-like mandibles (called forcipules) and other mouthparts.
Although compressed natural gas (CNG) is a fossil fuel like diesel, gas and coal, it is far different in terms of its impact on the natural environment.
Actually, that depends on what country you are in. In many countries, like the US and Australia, LPG is pure propane. However, New Zealand, Australia's close neighbour, has a mix. This article is a good read on the subject: Comparison between LPG & Natural Gas | Propane | Butane | Methane | LNG | CNG.