A : Presence of myelin sheath increases the rate of conduction of nerve fibre

B : Ionic channels are absent ib the area covered by myelin sheath therefore, depolarization occurs only at nodes of Ranvier, resulting in saltatory or jumping conduction.

(See the image to answer)

There are gaps callednodes of Ranvierbetween the schwann cells which are the onlyplaces wheredepolarisationcanoccur(due to Na+ entering the cell). This means that thedepolarisationjumps from onenodeto the next every 0.5 milliseconds via saltatory conduction, whichincreasesthespeedof conduction.Both Assertion and reason are correct so mark 1.