$\begin{array}{1 1} (a)\; \text{Dendritic end of one neuron to axonal end of another neuron} \\ (b)\; \text{Axon to cell body of the same neuron} \\ (c)\; \text{Cell body to axonal end of the same neuron } \\ (d)\; \text{Axonal end of one neuron to dendritic end another neuron} \end{array}$
