Cuales son los principales problemas de mantener un suelo fértil

are you referring to matrix mathematics!

true. earthquakes are felt whenever there is a slip around a fault in the rocks below the earth. this reorientation of faults create sesmic waves and is known as earthquake, the severity of which is measured in richter scale. these are more prominent in hilly regions as the rocks usually form faults to balance the pressures on it.

i beleive d is the right answer