Correct Answer - C
When a stimulus is applied at a site (e.g., point A ) on the polarised membrane, the membrane at the site A becomes freely permeable to `Na^(+)`.
This leads to a rapid influx of `Na^(+)` followed by the reversal of the polarity at that site, i.e. the outer surface of the membrane becomes negatively charged and the inner side becomes positively charged.
The polarity of the membrane at the site A is thus reversed and hence depolarised.
The electrical potential difference across the plasma membrane at the site A is called the action potential, which is in fact termed as a nerve impulse.
