**Core Concept**
The normal pH of tears is slightly alkaline, playing a crucial role in maintaining the health of the ocular surface. The pH of tears is regulated by the lacrimal gland and the conjunctiva, which work together to maintain a stable environment for the cornea.

**Why the Correct Answer is Right**
The normal pH of tears is approximately 7.2-7.5, which is slightly alkaline. This is achieved through the secretion of bicarbonate ions by the lacrimal gland and the conjunctiva. The bicarbonate ions help to neutralize any acidic substances that may come into contact with the ocular surface, thereby maintaining a stable pH environment. This is essential for the proper functioning of the cornea and the overall health of the eye.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as it is too acidic for the normal pH of tears. A pH of 6.5 would be considered abnormal and could potentially lead to ocular surface disease.
* **Option C:** This option is incorrect as it is too alkaline for the normal pH of tears. A pH of 8.5 would be considered abnormal and could potentially lead to discomfort and irritation of the ocular surface.
* **Option D:** This option is incorrect as it is a neutral pH, which is not typical for the normal pH of tears.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the normal pH of tears is slightly alkaline, and any significant deviation from this can lead to ocular surface disease. This is a crucial consideration for ophthalmologists and optometrists when assessing patients with ocular surface disorders.

**Correct Answer: B. 7.2-7.5**