**Core Concept**
Cereals are a significant source of dietary proteins, but they often lack certain essential amino acids. The amino acid profile of cereals is crucial for understanding their nutritional value.

**Why the Correct Answer is Right**
Cereals are generally rich in **non-essential amino acids**. However, among the options provided, if we consider common amino acid profiles, cereals tend to have a relatively higher amount of **glutamic acid**, an amino acid that can be conditionally essential under certain circumstances but is primarily non-essential.

**Why Each Wrong Option is Incorrect**
**Option A:** This choice is not specified, but typically, cereals are not uniquely high in any single essential amino acid compared to other protein sources.
**Option B:** Similarly, without the specifics, it's hard to judge, but cereals are not notably high in a particular essential amino acid that distinguishes them from other foods.
**Option D:** Again, lacking specifics, but generally, cereals are not highlighted for a specific essential amino acid content.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that while cereals provide important nutrients, their protein quality can be limited by a lack of **lysine**, an essential amino acid, making them less ideal as a sole protein source.

**Correct Answer:** D. Glutamic acid