The Rift Valley was formed by violent subterranean forces that tore apart the earth's crust.
B. Solar radiation is not impacted by a climate. It is determined by the location in terms of latitude.
Overcrowding and slums developed in many impoverished countries in the 20th century, mostly due to large migrations to cities from people looking for work.
The correct answer is - the change of the total volume of water in the Earth's system.
The total volume of the water in the Earth's system is pretty much the same, and for it to change, and change the levels of the water in the oceans and seas, the Earth will have to go over a totally new conditions where either a new influx of water will reach our planet, or the heat will increase and the water will evaporate, for now that is not a possibility.
