**Core Concept**
Adrenaline stimulates glycogenolysis through activation of specific enzymes. The underlying principle involves the activation of the sympathetic nervous system, leading to increased **cyclic AMP (cAMP)** levels. This increase in **cAMP** activates **protein kinase A (PKA)**, which in turn phosphorylates and activates key enzymes in the glycogenolysis pathway.

**Why the Correct Answer is Right**
Adrenaline acts on **glycogen phosphorylase**, the enzyme responsible for breaking down glycogen into glucose-1-phosphate. However, the correct answer is related to the activation of **phosphorylase kinase** by **protein kinase A (PKA)**, which then activates **glycogen phosphorylase**. The direct action of adrenaline is on **adenylyl cyclase**, increasing **cAMP** levels.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because while **glycogen synthase** is involved in glycogenesis, adrenaline's action is on glycogenolysis.
**Option B:** Incorrect as **debranching enzyme** is involved in a later step of glycogenolysis.
**Option D:** Incorrect because **phosphoglucomutase** is involved in converting glucose-1-phosphate to glucose-6-phosphate.

**Clinical Pearl / High-Yield Fact**
Remember that adrenaline's effect on glycogenolysis is part of the body's 'fight or flight' response, rapidly increasing glucose availability for energy.

**Correct Answer: C. Phosphorylase kinase**