Final answer:
The child can't understand that the boy is taller than the others, causing the flagpole to look different in length due to perspective, not because the flagpoles are actually of different lengths.
Step-by-step explanation:
The child is apparently unable to understand that the boy is taller than the others. If all flagpoles are of the same length, the perceived difference in the length of the flagpole held by one boy is likely due to the boy's height rather than the flagpole itself.
When the child observes that one flagpole looks different in length, this can be attributed to a perceptual error or misunderstanding of perspective. To comprehend this concept, the child would need to grasp that objects can appear larger or smaller depending on their distance from the viewer or based on the height of the person holding them, without actually being of different sizes.
Lastly, this situation illustrates how our sense of comparison and spatial awareness can be deceived by context, such as the height of the individuals in question.