</p> The total quantity of petroleum now thought to exist on Earth is about 14 trillion gallons.In weight that is only one-ninth as much as the total existing quantity of coal and,at the present moment,petroleum is being used up much more quickly.At the present rate of the use,the world's supply of petroleum may last for only thirty years or so.
! d, @% v [! A6 a# c There is another complication in the fact that petroleum is not nearly so evenly distributed as coal is.The major consumers of energy have enough local coal to keep going but are,however,seriously short of petroleum.The United Stated has 10 percent of the total petroleum reserves of the world in its own territory,and has been a major producer for decades.It still is,but its enormous consumption of petroleum products is now making it an oil importer,so that it is increasingly dependent on foreign nations for this vital resource.The Soviet Union has about as much petroleum as the United States,but it uses less,so it can be an exporter.
! s l- g: T7 k$ f0 Q! ^& h Nearly three-fifths of all known petroleum reserves on Earth is to be found in the territory of the various Arabic-speaking countries.Kuwait,for instance,which is a small nation at the head of the Persian Gulf,with an area only three-fourths that of Massachusetts and a population of about half a million,possesses about one-fifth of all the known petroleum reserves in the world.
& Z2 f. Z" }7 q3 i3 F( L0 z The political problems this creates are already becoming crucial.
% z: R7 I; K% \ 28Petroleum is unlike coal in the way.
+ o6 g7 ^2 j: N5 \! \ A.petroleum is found in sedimentary rocks and was probably formed from long-dead living organisms.2 q7 F5 \2 C) r& E, F0 Y
B.once the petroleum was obtained,it could be moved overland in freight trains.% _: d$ L5 @: n% h ?7 M: p
C.petroleum is not nearly so evenly distributed as coal is.8 R' G& Q0 `6 _1 x3 }2 p
D.petroleum exists on Earth in far greater quantities than coal does.
\' k% e* k0 C7 {0 A* A5 W 29The use of petroleum is greatly encouraged by.! ]7 _ I' _- u* W) q$ x6 ?
A.the fact that petroleum is lighter than water: ]; r O: Y8 ~* k7 Q
B.the fact that petroleum is the produce of the accumulating fatty matter of ocean organisms.
6 x+ }+ v2 `; P) B; _, w% Z C.the fact that obtaining and transporting petroleum is very convenient.2 T, |4 A8 z- O
D.the fact that the energy derived from burning petroleum is only 4 percent that of coal.* J$ n. o8 w% p- x
30Which of the following is a petroleum fraction made up of small molecules and one that therefore vaporized easily?8 n3 n: e! u+ G, X; s! y& O& q% X( _
A.kerosene. B.gasoline C.asphalt D.vapor |