I think its B or D, most likely D.
Answer:
A) being influenced by equal amounts of gravity and air resistance.
Explanation:
B) slowing down because of an unbalanced force of air resistance.
False - if it was slowing down, then the velocity would go down.
D) on the ground and is not falling anymore.
False - This would be mistaken as the answer but it is not because if the person is not falling anymore the horizontal line should be at the x-axis, meaning that there is no more velocity.
C) accelerating because of an unbalanced force of gravity.
False - The line would otherwise be going up or down.
I'm only adept in atomic makeup but my guess would be 13 electrons since they have a negative charge and protons have a positive one.