Marathon runners are encouraged to stop at water stations along the course to stay hydrated. However, occasionally a runner drinks too much water and suffers from hyponatremia, or "water intoxication". While water itself is not toxic, drinking too much can upset ion balance in the extracellular space.

Based on what you know about ions and nerve signaling, the levels of which important ion are most likely to be disrupted in hyponatremia?

A. hydrogen

B. potassium

C. calcium

D. sodium

E. oxygen

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.