he rock with the least carbon content is?

The rock with the least carbon content is sandstone. Sandstone is a sedimentary rock made up of sand-sized grains of mineral, rock, or organic material. Unlike coal and lignite, which are formed from plant matter, and marble, which is a metamorphic rock formed from limestone, sandstone does not contain any significant amount of carbon. To understand this, imagine sand at the beach - it's made up of tiny particles of minerals that have eroded from rocks and carried by water or wind to the beach. Similarly, sandstone is formed from the accumulation of sand-sized particles that have been deposited and cemented together over time. Because sandstone does not contain plant or animal matter, it does not have significant carbon content. Overall, sandstone is a rock that is primarily composed of mineral grains and has little to no carbon content.