**Core Concept**
Non-proliferative diabetic retinopathy (NPDR) refers to the initial stages of diabetic retinopathy, characterized by the presence of microvascular changes in the retina without significant proliferation of new blood vessels. This condition is a result of chronic hyperglycemia, leading to damage to the retinal capillaries and the formation of microaneurysms, hemorrhages, and hard exudates.

**Why the Correct Answer is Right**
The features of NPDR include microaneurysms, dot and blot hemorrhages, cotton wool spots, and hard exudates. These changes are due to the damage caused by advanced glycosylation end-products (AGEs) and the activation of various inflammatory pathways. The microvascular changes in NPDR are a result of the increased permeability of the retinal capillaries, leading to the leakage of fluid and proteins into the retina.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it is not a feature of NPDR.
**Option B:** This option is incorrect as it is a feature of NPDR, not a characteristic that distinguishes it from proliferative diabetic retinopathy (PDR).
**Option C:** This option is incorrect as it is not a direct feature of NPDR, but rather a potential complication of PDR.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the presence of neovascularization, vitreous hemorrhage, or tractional retinal detachment indicates the progression to proliferative diabetic retinopathy (PDR). The timely diagnosis and management of NPDR can prevent the progression to PDR and reduce the risk of vision loss.

**Correct Answer: D.**