**Core Concept**
Local anaesthetics are a class of medications used to prevent pain by interfering with the transmission of nerve impulses. They act by blocking the voltage-gated sodium channels in nerve membranes, which are essential for the initiation and propagation of action potentials.

**Why the Correct Answer is Right**
Local anaesthetics bind to the sodium channels in a reversible manner, preventing the influx of sodium ions into the neuron during an action potential. This inhibition of sodium influx blocks the depolarization of the nerve membrane, thereby preventing the generation and propagation of action potentials. The blockade of sodium channels is the primary mechanism by which local anaesthetics produce their analgesic effect.

**Why Each Wrong Option is Incorrect**
**Option A:** Inhibition of potassium channels is not the primary mechanism of action of local anaesthetics. While potassium channels are involved in the repolarization of the nerve membrane, local anaesthetics do not act by inhibiting these channels.
**Option B:** Local anaesthetics do not act by inhibiting calcium channels. Calcium channels are involved in the regulation of neurotransmitter release, but local anaesthetics do not affect these channels directly.
**Option C:** Local anaesthetics do not act by inhibiting GABA receptors. GABA receptors are involved in the regulation of inhibitory neurotransmission, but local anaesthetics do not affect these receptors directly.

**Clinical Pearl / High-Yield Fact**
Local anaesthetics can be classified into two main categories based on their chemical structure: ester-linked and amide-linked. Ester-linked local anaesthetics are more likely to cause allergic reactions, while amide-linked local anaesthetics are generally safer in this regard.

**Correct Answer:** B. Inhibition of sodium channels.