Mc Kay discovered Colorado stain in:
**Core Concept**
The question refers to the discovery of Colorado stain, which is related to **carcinoma**. Frederick McKay discovered this condition, and it is linked to **fluorosis**, a condition caused by excessive intake of **fluoride**.
**Why the Correct Answer is Right**
McKay's discovery in Colorado led to the identification of **fluoride** as the cause of **dental fluorosis**, also known as Colorado stain. This condition is characterized by **discoloration and pitting of teeth** due to excessive fluoride consumption.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect as McKay's discovery was specifically related to Colorado.
**Option B:** Incorrect as it is not associated with McKay's discovery.
**Option C:** Incorrect as it does not relate to the discovery of Colorado stain.
**Clinical Pearl / High-Yield Fact**
McKay's discovery is crucial in understanding the effects of **fluoride** on dental health, highlighting the importance of **moderate fluoride intake** to prevent **fluorosis**.
**Correct Answer:** D. Teeth