Final answer:
Gaseous fuels, like hydrogen, pose the greatest danger as they are more likely to ignite or explode compared to solid or liquid fuels due to their volatility and ease of dispersion.
Step-by-step explanation:
The question of which type of fuel is the most dangerous requires an understanding of the properties of different fuel states; solid, liquid, and gaseous. Gaseous fuels like hydrogen are more dangerous than their liquid or solid counterparts due to their propensity to ignite or explode under certain conditions. They are hard to contain, can easily spread into the environment, and mix with air to form explosive mixtures. For instance, hydrogen in its gaseous form presents not only storage difficulties but also serious explosion hazards. This contrasts with substances like gasoline, which are flammable but the liquid itself does not explode; rather, it is the vapors that are dangerous when mixed with air.
When considering the stability of various substances, those rated '4' in the given reference may detonate, indicating a very high potential for danger, whereas a rating of '0' indicates stability. Chemical forms also determine how a substance gets into the body and the harm it can cause. Chemical changes, like evaporation of liquids into vapors, can increase the risk of inhalation and explosion. Therefore, gaseous fuels are generally considered to present the highest level of danger in terms of immediate hazard and potential for damage.