Gene flow is partially responsible for
- genetic sameness.
-genetic variation.

genetic variation

Explanation:because Gene flow is all the alleles from each individual in the population, therefore there will be genetic variation.

option a is correct i.e.

explanation:

in context to the membrane of nerve impulse, the outer membrane of neuron is semi permeable that is only sodium ions can pass through the membrane i.e. smaller ions can pass through the membrane while larger ions cannot pass through it.