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.]