Answer:
B. four-crop rotations
Explanation:
the four-crop rotations was invented in the 18th century which means from January 1, 1701 to December 31, 1800. (1700s).
The correct answer is - B) convection currents in the mantle.
There's multiple tectonic plates on the surface on the planet, around 17 from what is known so far, but as the scientific methods are developing there might be few more discovered in the years to come.
These plates are all moving, only few cm per year, but on the long term it influences and changes everything on the surface on the Earth.
The movement of the plates is the result of the convection currents in the mantle layer beneath. These convection currents are essentially the combination of the high temperatures, high pressures, and viscous metals, and they managed to break up the crust on the surface, and with its push force, they are slowly moving the plates.
With the movement of the plates and their collisions and moving away, lots of earthquakes and volcanoes are appearing all over the plate boundaries.
Welcome to Earth, where we have the best pies!
Educated people don't need to be in Iran. Iran doesn't provide colleges or any type of higher education that awards degrees. Iran is also a dangerous place, especially for women, seeing as you have gangs or terrorist groups such as The Taliban or Isis.
Well there's is frozen sea weed and there is plankton and hair grass