[求助]OG11－6 黄色书

Not all life depends on energy from sunlight.Microbial life has been found in bedrock more than five kilometers below the surface of the Earth, and bacteria have been found on the deep ocean floor feeding on hydrogen and other gases rising from the interior of the Earth through vents in the ocean floor.

The statements above, if true, best support which of the following as a conclusion?

(A) The location in the bedrock where microbial life was found was not near a system of volcanic vents through which hydreogen and other gases rose from the interior of the Earth.

(B) Bacteria are able to exist at the molten center of the Earth.

(C) A thotough survey of a planet's surface is insufficient to establish beyond a doubt that the planet contains no life.

(D）Life probably exists on Sun-orbiting comets, which arecold agglomeration of space dust and frozen gases.

(E) Finding bacterial remains coal and oil would establish that the bacteria had been feeding on substances that had not been produced from the energy of sunlight.

问题：不理解C选项的意思。能否帮我解释一下？在此表示感谢！

beyond a doubt 字面理解就是：超出doubt之外，不就是“不需要怀疑”的意思嘛~~