This portion of the vestibular apparatus is responsible for dynamic equilibrium.
select one:
a. semicircular canals
b. sensory cells
c. vestibule
d. otoliths

Semicircular canals

Explanation:

Ear is one of the important sense organ responsible for hearing and equilibrium. Human ear is divided into three parts: outer ear, middle ear and inner ear.

Inner ear is mainly responsible for the equilibrium of the body. Vestibular apparatus together with semicircular canals is responsible for the dynamic equilibrium of the body. Dynamic equilibrium  involves head rotation and vertical movements of the body.

Thus, the correct answer is option (a).  

1. glaciers are melting

2. more water going into ocean (water's such as fresh waters, etc)