**Core Concept**
The question is testing the knowledge of a vitamin deficiency disorder associated with a specific dietary staple. The correct answer will be based on the nutritional content of the mentioned cereals and the resulting deficiency in a particular vitamin.

**Why the Correct Answer is Right**
Beriberi is a classic example of a vitamin deficiency disorder caused by a lack of thiamine (Vitamin B1). In people who consume polished rice as their staple diet, the bran and germ layers, which are rich in thiamine, are removed. This results in a significant reduction of thiamine in the diet, leading to beriberi. Thiamine plays a crucial role in the decarboxylation of alpha-keto acids in the Krebs cycle, and its deficiency affects the production of ATP.

**Why Each Wrong Option is Incorrect**
* **Option A:** While pellagra is a vitamin deficiency disorder, it is caused by a lack of niacin (Vitamin B3) and is associated with a diet lacking in tryptophan, not a specific cereal staple.
* **Option B:** Scurvy is a disease caused by a lack of vitamin C, not a vitamin deficiency disorder associated with a cereal staple.
* **Option C:** Rickets is a disease caused by a lack of vitamin D or calcium, not a vitamin deficiency disorder associated with a cereal staple.

**Clinical Pearl / High-Yield Fact**
In areas where polished rice is a staple food, beriberi is a common public health problem. This highlights the importance of consuming whole grains and bran-rich foods to prevent thiamine deficiency.

**Correct Answer:** C. Beriberi.