**Core Concept**
Electromyography (EMG) is a diagnostic tool used to assess the electrical activity of muscles. Denervation refers to the loss of nerve supply to a muscle, leading to changes in muscle physiology and electrical activity. EMG can detect these changes, helping to diagnose conditions such as motor neuron disease, peripheral neuropathy, or muscle damage.

**Why the Correct Answer is Right**
Denervation on EMG typically presents with changes in the electrical activity of the muscle, including:
* **Polyphasic potentials**: These are action potentials that have more than two phases, indicating abnormal muscle fiber recruitment and contraction patterns.
* **High-frequency discharge**: Denervated muscles exhibit high-frequency discharge, which is a characteristic feature of denervation.
* **Fibrillation potentials**: These are spontaneous discharges of individual muscle fibers, which occur in denervated muscles.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because **insertional activity** is actually a normal finding on EMG, representing the electrical activity of muscle fibers when a needle electrode is inserted into the muscle. It does not suggest denervation.

**Option B:** This option is incorrect because **sharp waves** can be seen in both normal and denervated muscles. Sharp waves are a type of action potential that can occur in response to muscle insertion or other stimuli.

**Option C:** This option is incorrect because **positive sharp waves** are actually a feature of denervation, indicating the presence of fibrillation potentials or positive sharp waves.

**Clinical Pearl / High-Yield Fact**
When interpreting EMG results, it's essential to consider the clinical context and correlate the findings with the patient's symptoms and medical history. Denervation on EMG can be a sensitive indicator of motor neuron disease or peripheral neuropathy, but it's not specific and requires careful interpretation.

**Correct Answer: A. Insertional activity is a normal finding on EMG and does not suggest denervation.**