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?

【选项】A thorough survey of a planet's surface is insufficient to establish beyond a doubt that the planet contains no life.