<span>Sumerians built walls using the natural resource they were surrounded with, which was namely clay. They used this clay to create fired mud-bricks, as there was not any other building stone available at the time. However, the clay mud-bricks proved to be a solid structure for town fortification.</span>
The correct answer is: desertification.
Desertification is a process in which a land which was not a desert before, becomes one. This process can include drying out- through for example loss of water source, such as river diversion- and the loss of vegetation.
Photosynthesis is a process in which a plant uses sunlight to create food, using CO2 and water.
The limbs of the organisms are similar because they are formed in similar ways during embryonic development and share similar arrangements.
