The measurement of the acuteness or sharpness of vision is:

A) color vision test.
B) ultrasonography.
C) tonometry.
D) visual acuity.

Visual acuity is the measurement of the sharpness or clarity of vision, usually measured using an eye chart. Color vision tests measure the ability to distinguish between different colors, ultrasonography is the use of sound waves to image internal structures of the body, and tonometry measures the intraocular pressure of the eye.