Apopulation of mice lives in a city. the largest mice tend to be killed by predators and the smallest mice cannot compete for food. what type of selection is this

There are many types of natural selection like direct selection, disruptive selection and stabilizing selection.
The situation given is that a population of mice lives in a city. The largest mice tend to be killed by predators and the smallest mice cannot compete for food.
The type of selection here is stabilizing selection. It is a type of natural selection in which there is decrease in genetic diversity as the population stabilizes.

option a is correct i.e.

only sodium ions can pass through the membrane.

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.