How and why does the population change over time using natural selection

Explanation: Natural selection is a cause of evolution. So over time, organisms can start to evolve due to artificial selection. Natural selection, sometimes referred to as "survival of the fittest," is a mechanism for the evolution of a population to become better adapted for survival in a specific environment. This means that organisms with traits that are best suited for the environment will pass these traits to their offspring.

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.