**Core Concept**
The acidic property of certain amino acids is attributed to the presence of a specific functional group attached to the alpha-carbon (α-C) of the amino acid. This functional group is responsible for the characteristic acidic behavior of these amino acids.

**Why the Correct Answer is Right**
The acidic property of the α-C of certain amino acids is due to the presence of a carboxyl group (-COOH). This carboxyl group is a strong acid, capable of donating a proton (H+ ion), thereby exhibiting acidic behavior. The presence of the carboxyl group is a result of the α-carbon being bonded to a carbonyl group, which is a key structural feature of amino acids with acidic properties.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify the functional group responsible for the acidic property. Although it mentions a specific amino acid, it lacks the necessary detail to accurately explain the phenomenon.
* **Option B:** This option is incorrect because it does not identify the correct functional group responsible for the acidic property. It may be a distractor, aiming to mislead the test-taker into choosing an incorrect answer.

**Clinical Pearl / High-Yield Fact**
Amino acids with acidic properties, such as aspartic acid and glutamic acid, are important in various physiological processes, including neurotransmission and muscle contraction. Understanding the acidic properties of these amino acids is crucial for grasping their roles in the body.

**Correct Answer: C. The carboxyl group (-COOH) attached to the α-C of certain amino acids is responsible for their acidic property.**