1.   Many animals have a single lens used to focus light on to a plate able to convert it into nerve impulses.

2.   If the mirror is made with a convex surface, it can be used to focus X-rays.

3.   As a result, the process occurs in a vacuum and mirrors are used to focus the light.

4.   The banter is less a sign of disagreement than strategy Posada uses to focus Hernandez.