The ________, shown at letter I in the figure, controls the amount of light that enters the eye. 

Premature gray hair:

A) L67.1. B) L67.9. C) L67.0. D) L67.8.

Which of the following converts cardiac arrhythmia into normal sinus rhythm?

a. Ventricular fibrillation b. Cardioversion c. Noninvasive Holter monitor d. None of the above