How do organisms living in the intertidal zone use byssal hair?
A. As a net to help capture food
B. As an anchor against tidal action
C. As protection against harsh sunlight
D. As a filter to remove salt from water

B) As an anchor against tidal action

Explanation:

Byssal hairs (or threads) are used to anchor organisms to rocks and other solid surfaces to protect them from wave shock (tidal action).

These hairs/threads stretch out in many directions to hold the organism in place. Mussels are an example of an organism that uses byssal threads.

[This answer was pasted from another question I also answered. You can find it here:  As I said, the original answer was also written by me.]

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.

answer; increases;