What do stabilizing selection and disruptive selection have in common? ?

Variation

Explanation:

In natural selection, variation happens to produce more fit organisms. The natural selection is a different type such as stabilizing selection, directional selection, and disruptive selection. In both cases, variation occurs but the variation rate is different.  Therefore, the common thing between stabilizing selection and disruptive selection is variation. The variation rate is slow in stabilizing selection. Hence in this selection less phenotype characters are seen. In disruptive selection, variation is random and extreme. Thus more phenotype individuals are formed due to disruptive selection.

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.