What is the primary function of the ciliary muscles in the human eye?

In humans,corneal transplants are rarely rejected. This is because:

The diameter of the pupils is regulated by the muscle fibres of ...........

The chemical used by doctors to dilate the pupil for examination is

Answer briefly:
$(a)$ How do you perceive the colour of an object?
$(b)$ Which part of our body helps us in maintaining the body balance?
$(c)$ How does the eye regulate the amount of light that falls on the retina?

Select the correct option for the blind spot.