Rna contains the nitrogenous base instead of thymine which is found in dna.
a. glycosamine
b. uracil
c. phosphate
d. ribose

RNA contains the nitrogenous base Uracil (B) instead of thymine which is found in DNA. RNA also contains ribose (D). This is the main difference between RNA and DNA. RNA is one of three biological molecules that is found in every cell in all forms of life. DNA and Proteins are the other two biological molecules. DNA and RNA carry the genetic material that allows organisms and cells to divide and multiply. Proteins are the hard workers of the cell. 

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.

Ibelieve its b but u might have to