Fuel fuel. They are also used to start a coal fire. Liquid fuels are combustible or energy-generating molecules that can be harnessed to create mechanical energy, usually producing kinetic energy; they also must take the shape of their container. It is the fumes of liquid fuels that are flammable instead of the fluid. Most liquid fuels in widespread use are derived from the fossilized remains of dead plants and animals by exposure to heat and pressure inside the Earth's crust. However, there are several types, such as hydrogen fuel (for automotive uses), ethanol, jet fuel and bio-diesel which are all categorized
Interlanguage fossilization opinion. The term, borrowed from the field of paleontology, conjures up an image of dinosaurs being enclosed in residue and becoming a set of hardened remains encased in sediment. The metaphor, as used in SLA literature, is appropriate because it refers to earlier language forms that become encased in a learner's interlanguage and that, theoretically, cannot be changed by special attention or practice of the target language. Despite debate over the degree of permanence, fossilization is generally accepted as a fact of life in the process of SLA. Many researchers have attempted to explain this. Workers have attempted to discover: