When a neuron is in resting state $I$ not conducting any impulse,the axonal membrane is :

Which of the following statement/s is/are correct with respect to generation and conduction of nerve impulse?
i. The resting potential difference is $-70 \text{ mV}$.
ii. The voltage-gated $Na^{+}$ and $K^{+}$ channels operate together and are self-closing.
iii. At the peak of action potential,the potential difference rises to $+30$ to $+60 \text{ mV}$.
iv. In medullated nerve fibre,the action potential is conducted as a wave of membrane depolarization.
v. The resting potential is maintained by the closure of gated channels of $Na^{+}$ and $K^{+}$.

$A$: Presence of myelin sheath increases the rate of conduction of nerve impulse.
$R$: Ionic channels are absent in the area covered by myelin sheath; therefore,depolarization occurs only at the nodes of Ranvier,resulting in saltatory or jumping conduction.

When a neuron is in resting state,$i.e.$,not conducting any impulse,the axonal membrane is

Which of the following statements is/are correct?
$(a)$ The electrical potential difference across the resting plasma membrane is called the resting potential.
$(b)$ $Na^+$ ions are responsible for the generation of an action potential.
$(c)$ $A$ nerve impulse is an action potential.

What does the extracellular fluid of an axon contain in a resting state?