Final answer:
The correct answer is a) Receptor. Receptors are specific proteins on the target cell's surface that bind to signaling molecules or ligands, initiating an intracellular response, such as the electrical signals transmitted by axons in neurons.
Step-by-step explanation:
In order for a target cell to receive a signal, it must possess a receptor specific to the signaling molecule. Receptors are proteins that bind to signaling molecules, known as ligands, and initiate a response within the cell. This interaction is highly specific, meaning a receptor will typically bind only to its specific ligand. Among the options provided, a receptor is the correct answer. In the context of neural cells, when a neuron transmits an electrical signal to a target cell, it is the axon that carries this signal to the target cell's receptors.