The dark areas on the map show the distribution of coral reefs around the world. What explanation best describes why the distribution of coral reefs is limited to the areas shown on the map? A. Competition for space is lowest in waters along the equator.
B. Equatorial waters provide some of the clearest water for symbiotic algae to produce energy.
C. Predation is lowest in areas along the equator because of increased rates of decomposition.
D. The corals need the strong water currents found here in order to find sufficient mates.

answer and explanation;

volcanic rocks are igneous rocks which form from lava, molten rock which has been thrust out of a volcano onto the surface of a rocky body such as an asteroid, planet, or dwarf planet.  

plutonic rocks are igneous rocks which form from subterranean chambers of molten rock or magma. plutonic rocks make up the base of continental crust as well as oceanic crust. their slow rate of formation causes them to be coarse grained since there is plenty of time for large crystals to form before the magma solidifies into rock.

the textural difference is that plutonic rocks are more coarse grained than volcanic rocks. plutonic rocks are coarse grained while volcanic are fine grained ; glassey or fragmental. since fine and coarse are adjectives the decision as to whether a rock is fine or coarse grained is generally made on the bases of whether or not the individual crystals can be seen in most if the rock.