The rental agencies determine the rules for that. Most rental companies will not rent to anyone under the age of 25. Some will rent to people 21 to 24 years old, but charge a premium rate. The only time I have ever heard of a rental car company renting to an 18-year old is to a member of the military.
1 The lens is a soft, transparent, spherical structure that is suspended within the eye, just behind the pupil. 2  The lens is responsible for focusing light coming in through the pupil onto the retina in the back of the eye.
In optical terms, the anatomical pupil is the eye's aperture and the iris is the aperture stop. The image of the pupil as seen from outside the eye is the entrance pupil, which does not exactly correspond to the location and size of the physical pupil because it is magnified by the cornea.