**Core Concept**
A true diabetic cataract, also known as a "snowflake" cataract, is a characteristic type of cataract that occurs in diabetic patients. It is caused by the accumulation of sorbitol in the lens, leading to osmotic changes and eventual cataract formation.

**Why the Correct Answer is Right**
The correct answer is a "snowflake" cataract because it is the most characteristic type of cataract seen in diabetic patients. This type of cataract is caused by the accumulation of sorbitol, a sugar alcohol that is produced when glucose is metabolized in the lens. The accumulation of sorbitol leads to osmotic changes, causing water to enter the lens and leading to lens swelling and eventual cataract formation. The snowflake appearance is due to the characteristic white or grayish opacities that are scattered throughout the lens.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because a "oil drop" cataract is a type of cataract that is caused by a posterior capsular rupture, not by diabetes.
* **Option B:** This option is incorrect because a "soot and dust" cataract is a type of traumatic cataract, not a type of cataract associated with diabetes.
* **Option C:** This option is incorrect because a "oil drop" cataract is a type of cataract that is caused by a posterior capsular rupture, not by diabetes.

**Clinical Pearl / High-Yield Fact**
It's essential to recognize the characteristic "snowflake" appearance of diabetic cataracts, as this can help in differentiating them from other types of cataracts. Diabetic cataracts are often bilateral and may be associated with other systemic complications of diabetes, such as retinopathy and nephropathy.

**Correct Answer:** C.