Although the prevailing supposition has been that it is too hot for microorganisms to survive deep below the Earth's surface, some scientists argue that there are living communities of microorganisms there that have been cut off from surface life for millions of years.These scientists base their argument on the discovery of living microorganisms in samples of material that were taken from holes drilled as deep as 1.74 miles.
The scientists' argument depends on which of the following assumptions?
(A)The microorganisms brought up were of a species that is related to those previously known to science.
(B)No holes have been drilled into the Earth's surface to a distance deeper than 1.74 miles
(C)The microorganisms did not come from surface soil that came into contact with the drilling equipment.
(D) The stratum from which the samples came has been below the surface of the Earth ever since the Earth came into existence.
(E) The temperature at the bottom of the holes drilled was not significantly hotter than that of the hottest spots on the Earth's surface.
答案：C