Ploughing and turning over the soil aerates the soil so the roots of plants are able to thrive well. Ploughing the roots of leguminous plants back to the soil returns nutritents and organic matter to the soil organically rather than using synthetic fertilisers which are potentially hazardous to the environment.
Water is polar and the positive and negative ends of the molecule attract each other.
Answer:
Galaxies rotate in their center with parts of galaxies that are far away from centre.
Explanation:
Galaxies move throughout the space. It rotates around its center with the portions of galaxy that are far from the center and moves relatively slowly from other objects near the center.
Because of the Big bang explosion because of which the Universe have expanded, galaxies are going away from other galaxies. The galaxy cluster also moves around the cluster center.
A closed system is a system that makes no physical or chemical exchanges with its environment. Of these systems provided as choices (tree, human, clock, car), only a clock does not make exchanges with the environment, except for energy.
Therefore, of that list, only a clock would be a closed system.
Hope that helped! =)
