A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?

The human eye can focus on objects at different distances by adjusting the focal length of the eye lens. This is due to

1. presbyopia
2. accommodation
3. near-sightedness
4. far-sightedness

The least distance of distinct vision for a young adult with normal vision is about

1. 25 m
2. 2.5 cm
3. 25 cm
4. 2.5 m

The change in focal length of an eye lens is caused by the action of the

1. pupil
2. retina
3. ciliary muscles
4. iris