What is the definition of 'lente' in the context of eye protection equipment?

I - It is the transparent part of an eye protection element through which the user sees.
II - It is a lens that reduces the intensity of visible light and ultraviolet and infrared radiation to predetermined levels.
III - It is a lens that darkens when exposed to ultraviolet light and deactivates when removed from it.
IV - It is a lens without dioptric power.
a) I and II are correct.
b) II and III are correct.
c) III and IV are correct.
d) I and IV are correct.