**Core Concept**
Western blot technique is a laboratory method used to detect and analyze proteins in a sample. It involves separating proteins by size using gel electrophoresis, transferring them to a membrane, and then detecting specific proteins using antibodies.

**Why the Correct Answer is Right**
The correct answer is an antibody-based probe. In Western blotting, a primary antibody is used to specifically bind to the target protein on the membrane. This binding is often followed by a secondary antibody that is conjugated to an enzyme or a fluorescent marker, allowing for detection and quantification of the target protein. The primary antibody is usually specific to a particular antigenic determinant (epitope) on the protein, enabling the detection of the protein of interest.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is likely a distractor, as Western blot does not typically use probes that are not antibody-based. While there are other types of blotting techniques, such as Southern blot (DNA) and Northern blot (RNA), the question specifically mentions Western blot, which is used for proteins.

**Option B:** This option might be a distractor, as some types of blotting techniques might involve probes that are not antibody-based, such as radioactive probes. However, Western blot specifically uses antibodies as probes.

**Option C:** This option is incorrect, as Western blot does not use probes that are not antibody-based, such as DNA probes.

**Clinical Pearl / High-Yield Fact**
A key aspect of Western blotting is the use of specific antibodies to detect target proteins. This technique is widely used in research and clinical diagnostics for identifying and quantifying proteins, such as in the diagnosis of infectious diseases (e.g., HIV, Lyme disease) and autoimmune disorders (e.g., rheumatoid arthritis).

**Correct Answer: A. Antibody-based probe.**