Can a persons genotype be determined by thier phenotype.? why or why not.?

You can't always figure out genotype from phenotype with a dominant trait because dominant traits can happen with two different genotypes.

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.

answer; i believe its echoic memory,it is believed to last three to four seconds; good luck