Final answer:
Emmetropia is the state where the eye is at rest and can focus on distant objects accurately, with the light focusing directly on the retina. This is the correct answer to the student's question, which is not to be confused with myopia or hyperopia, which are vision defects.
Step-by-step explanation:
A state in which the eye is relaxed and focused on an object more than 6m (20ft) away is known as emmetropia. In this condition, the eye's optical system is perfectly adjusted so that light rays from distant objects are focused directly on the retina, creating a clear image without the need for accommodation. This contrasts with conditions such as myopia (nearsightedness), where distant objects appear blurred because the images focus in front of the retina, and hyperopia (farsightedness), where nearby objects are blurry because the images focus behind the retina. The correct answer to the student's question is d) Emmetropia.