If an object reflects light toward the eye then that object can be seen.
Light is focussed on the retina.
If an object can be focussed on the retina, it can be seen.
what does it mean if an object can be focussed on the retina?

[A] sunlight
[B] lowered energy cost
[C] it has density
[D] it is a rainbow
[E] observe it
[F] Change colors
[G] it is invisble
[H] it can be seen