**Core Concept**
The limiting amino acid in a food source refers to the essential amino acid that is present in the lowest quantity, making it the rate-limiting factor for protein synthesis. In the context of Bengal gram, also known as chickpeas, the limiting amino acid is crucial for understanding its nutritional value and potential health benefits.

**Why the Correct Answer is Right**
Bengal gram is a rich source of protein and essential amino acids, but it is often deficient in the amino acid methionine. Methionine is an essential amino acid that plays a vital role in various bodily functions, including protein synthesis, detoxification, and methylation reactions. The low methionine content in Bengal gram makes it a limiting amino acid, which can be addressed by combining it with other legumes or grains that are rich in methionine.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as it does not specify the limiting amino acid in Bengal gram. Without further context, it is difficult to determine the correct answer.
* **Option B:** This option is incorrect as it does not accurately identify the limiting amino acid in Bengal gram. While Bengal gram is a rich source of protein, it is not deficient in the amino acid lysine.
* **Option D:** This option is incorrect as it does not accurately identify the limiting amino acid in Bengal gram. While Bengal gram is a good source of essential amino acids, it is not deficient in the amino acid threonine.

**Clinical Pearl / High-Yield Fact**
Remember that the limiting amino acid in Bengal gram is methionine, which can be addressed by combining it with other legumes or grains that are rich in methionine. This knowledge is essential for understanding the nutritional value of Bengal gram and its potential health benefits.

**Correct Answer:** C. Methionine