Transmission of a signal within a neuron in one direction only, from dendrite to axon terminal is carried out by the opening and closing of voltage-gated ion channels, which cause a brief reversal of the resting membrane potential to create an action potential.
If you use a mixture of formats in a single document, it can be confusing to the reader. This is the exact opposite of what formatting is supposed to do.
Answer: c. Each line of the document has different formatting applied to it.