D is the answer because i took the same test and got it right
Answers A and D are found on my prescription bottles.
Answer: The correct answer is (D) Both A and B
Explanation:
When an axon is depolarized at halfway to the threshold level,the action potential will be generated that would travel 'downstream' i.e towards the synapse and 'upstream' i.e back towards the cell body. This is because both channels on either sides are not under refractory period,i.e they are open.