Suppose that in goats, an independently sorting autosomal allele that produces a bearded phenotype is dominant in males and recessive in females. the symbol bb represents the bearded allele and b represents the beardless allele. the autosomal allele for a black coat (w), which also independently assorts, is dominant over the allele for white coat (w). match each set of progeny phenotypes and proportions to the parental cross that produced that set.

B+ Bb Ww male × B+ Bb Ww female Because beardedness and coat color independently assort, we can treat them independently. The difference between this cross and a dihybrid cross is that the bearded allele B b is dominant in males and recessive in females. So we deal with male and female progeny separately. For each sex, then, we should get a typical dihybrid ratio. In males, the dominant phenotype is bearded, so we should get ¾ bearded, ¼ beardless. In females the dominant phenotype is beardless, so we should get ¾ beardless and ¼ bearded. Each sex will have ¾ black and ¼ white coats.

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.