Which comparison is useful for identifying a small error in an object's proportion?

Correct answer: Compare part lengths with the overall form

The governing concept is proportion, meaning the relationship of each part to the whole and to other parts. To locate a small error, compare a part’s length, width, or position with the overall bounding form rather than judging it in isolation. For example, a handle can look plausible alone but be too long compared with the vessel. The cast shadow, paper thickness, or pencil colour does not directly test object proportion, so option A is correct.