The direction along the radius and directed away from the center is known as radial direction.
The velocity is highest in the radial direction pointing away from the center, this is because of the reason that when the particle executes its motion in the direction that is radial, then it is not acted upon by any force that opposes the motion of the particle and thus there is no obstruction to the velocity of the particle and it is therefore, the highest in the radial direction.
The correct answer is "D. This device converts the chemical energy of hydrogen into electricity through a chemical reaction with oxygen or another oxidizing agent."
