For the propagation of a nerve impulse along a nerve fiber,what is the sequence of change in the electrical potential difference across the axolemma?

When a neuron is in resting state,$i.e.$,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 $K^{+}$.

$A$ : The imbalance in the concentration of $Na^+, K^+$ and proteins generates the resting potential.
$R$ : To maintain the unequal distribution of $Na^+$ and $K^+$,the neurons use electrical energy.

Conduction of an impulse along the axon is associated with the

During the resting state of a neural membrane,if diffusion is allowed due to concentration gradients,which ion is allowed to enter the cell?