Concept:The part of the eye that physically encloses and protects the eyeball from injury is the tough outer layer called the sclera.
Explanation:The labelled parts in the diagram are: I – iris, II – eyelashes, III – pupil, and IV – sclera.
Among these, the sclera is the tough, white, fibrous outer coat of the eyeball.
It maintains the shape of the eye and protects its delicate internal structures from damage.
The eyelashes (II) also give some protection from dust and insects, but they are not the main protective coat of the sense organ itself.
Therefore, the labelled part that directly protects the organ is the sclera, which is represented by label IV.
Answer:D. IV
