Answer : The density of an object is, 
Solution : Given,
Mass of an object = 60 g
Volume of an object = 
Formula used :

Now put all the given values in this formula, we get the density of an object.

Therefore, the density of an object is, 
The diameters of the spheres are 72.5 meters square
Answer:
The filter bed is cleaned by occasional backwashing ;-; im sorry if this isn't a great answer but I tried
Answer:
Fault-block mountain
In geography, fault-block mountains arise when the Earth's crust pulls apart and divides. Some parts of the Earth are pushed upwards whereas the other moves downward forming a divergent boundary. In geological studies, a divergent boundary can be described as a linear feature which arises due to plate tectonics which are being pulled apart from each other. Hence, fault-block mountains are most likely to be seen in a divergent boundary.
Most active divergent plate boundaries occur between oceanic plates and exist as mid-oceanic ridges. Divergent boundaries also form volcanic islands, which occur when the plates move apart to produce gaps that molten lava rises to fill.
Answer:
C overgrazing is the answer