Nucleotides make up the structure of DNA. Which of these distinguishes each of the particular nucleotides from each other?

DNA is made up of molecules called nucleotides

Explanation:

Nucleotides containe a phosphate group, A sugar group and a nitrogen group. The four types of nucleotide bases are adenine (A,thymine(T),Guanine (G) ,cytosine(C) .In order to determine Genetic code

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.