18.Most geologists believe oil results from chemical transformations of hydrocarbons derived from organisms buried under ancient seas. Suppose，instead， that oil actually results from bacterial action on other complex hydrocarbons that are trapped within the Earth. As is well known， the volume of these hydrocarbons exceeds that of buried organisms. Therefore， our oil reserves would be greater than most geologists believe.

　　Which of the following， if true， gives the strongest support to the argument above about our oil reserves？

　　（A） Most geologists think optimistically about the Earth's reserves of oil.

　　（B） Most geologists have performed accurate chemical analyses on previously discovered oil reserves.

　　（C） Ancient seas are buried within the Earth at many places where fossils are abundant.

　　（D） The only bacteria yet found in oil reserves could have leaked down drill holes from surface contaminants.

　　（E） Chemical transformations reduce the volume of buried hydrocarbons derived from organisms by roughly the same proportion as bacterial action reduces the volume of other complex hydrocarbons.

　　keys： ACBDB AAADE DCABE BBE