The main problem with use of conventional natural gas as a transportation fuel is
a. the expensive engine modifications required to convert an automobile for use of natural gas
b. the fact that it has higher CO2 emissions than gasoline produced from conventional oil
c. the very low reserves, which could supply U.S. needs for less than 25 years
d. the fact that not many fueling stations exist at present
e. it can only be obtained by fracking
D
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Which of the following factors are represented by the "P" and "E" in Thornthwaite's P/E ratio?
A. potential sunlight and energy B. precipitation and energy (available) C. potential sunlight and evaporation D. precipitation and evaporation
The oldest australopithecines were _________________________. Fill in the blank(s) with the appropriate word(s)
North America is closest to the sun, during
A. aphelion, which occurs in early January. B. perihelion, which occurs in early July. C. aphelion, which occurs in early July. D. perihelion, which occurs in early January.
Which of the following minerals would likely crystallize early from magma?
a. mafic minerals b. quartz c. muscovite d. potassium