An adaptation that helps an organism survive in its environment would be an adaptation that helps this organism get food/water, hide from predators, not loose too many water or nutrients, etc.
A green lizard living in red and brow rocks would cause a great contrast between the colors, putting the lizard in evidence and making it easier for predators to find it. Therefore, A is incorrect.
The adapted leaves of plant from the tundra will be small and waxy, but not too thin as it will try to keep more water inside it than being lost in transpiration. Therefore, D is also incorrect.
An animal that lives in the desert can't have a thick coat of fur because it will make the animal be super heated, causing loss of water that is so important to keep in a desert. So B is incorrect too.
In deserts that are no water easily available, so a plant can have a long root system in order to get water from deep below the surface of the ground. Therefore, the correct answer is C. A long root system in a desert plant