Based on the information provided, if only paper clips W and X moved toward the magnet, we can infer that the effective magnetic range is limited to the distances at which these specific paper clips are located.
Without the actual picture to determine which paper clips were at which distances, I can’t definitively tell which answer is correct. However, if you know the distances of W and X from the magnet and want to determine the maximum distance where the magnet is effective, you would select the distance that is still less than or equal to the farthest distance from which W or X was able to move toward the magnet.
Assuming the distances of W and X are stipulated in the question options, you would choose the maximum distance at which they moved toward the magnet.
To select the correct answer, please ensure that you know the distances of W and X from the magnet. If you have that information, select the option corresponding to the farthest distance where those clips were effective in moving toward the magnet.