Fuel were present at the sites. As a fuel, wood has remained in use up until the present day, although it has been superseded for many purposes by other sources. Wood has an energy density of 10–20 MJ/kg. Recently biofuels have been developed for use in automotive transport (for example Bioethanol and Biodiesel), but there is widespread public debate about how carbon efficient these fuels are. Fossil fuels are hydrocarbons, primarily coal and petroleum (liquid petroleum or natural gas), formed from the fossilized remains of ancient plants and animals by exposure to high heat and pressure in the absence of oxygen
Interlanguage fossilization Interlanguage fossilization Interlanguage fossilization is a phenomenon of second language acquisition (SLA) in which second language learners develop and retain a linguistic system, or interlanguage, that is self-contained and different from both the learner's first language and the target language. This linguistic system has been variously called interlanguage, approximative system, idiosyncratic dialects, or transitional dialects. According to Corder this temporary and changing grammatical system, interlanguage, which is constructed by the learner, approximates the grammatical system of the target language. In the process of second language acquisition, interlanguage continually evolves into an ever-closer approximation of the target language, and ideally should