preferred embodiments of the invention preferred energy preferred example preferred examples preferred expression preferred feature preferred features preferred first preferred food preferred form preferred format preferred forms preferred fuel preferred gas preferred glass preferred group preferred groups preferred habitat preferred high preferred him preferred host preferred hotel preferred hotels preferred i preferred implementation preferred inert preferred initiator preferred instrument preferred ionic preferred it preferred language preferred learning preferred length preferred level preferred levels preferred liquid preferred location preferred locations preferred low preferred lower preferred lubricant preferred lubricants preferred manner preferred material preferred materials preferred maximum preferred me preferred meaning preferred means preferred media preferred medium preferred metal preferred metals preferred method preferred method of communication preferred method of payment preferred methods preferred mode preferred mode of administration preferred model preferred modes preferred molar preferred molecular preferred more preferred name preferred natural preferred network preferred networks preferred nitrogen preferred not preferred number preferred oil preferred one preferred operating preferred option preferred optional preferred options preferred organic preferred orientation preferred other preferred over other preferred parameters preferred partner preferred partners preferred pattern preferred payment preferred ph preferred pharmaceutical preferred place preferred plant preferred plastic preferred platform preferred polymer preferred position preferred positions preferred practice preferred pressure preferred prey preferred process