Swamps or maybe those in the desert. In swamps, the soil is too loose for animals to burrow without it caving in. In deserts, since the climate "rising" its getting to hot and dry for animals to burrow without the sand caving in when an animal walks above it.
Liquid water, which is necessary for life as we know it, continues to exist on the surface of Earth because the planet is at a distance, known as the habitable zone, far enough from the Sun that it does not lose its water to the runaway greenhouse effect.
Answer: A, burning fossil fuels
B. The levels of classification increased. Previously there were only 2 domains of life, Bacteria and Eukarya, but an additional domain and Kingdom were added when the distinction of Archaea was observed.
