但是不是所有的作者目的题，都只是段落的第一句话。每个段落的topic sentence 位置不一样，或者说，每个例子对应的topic sentence 位置不一样。我们再来看一个例子，
Sensitivity to physical laws is thus an important consideration for the maker of applied-art objects. It is often taken for granted that this is also true for the maker of fine-art objects. This assumption misses a significant difference between the two disciplines. Fine-art objects are not constrained by the laws of physics in the same way that applied-art objects are. Because their primary purpose is not functional, they are only limited in terms of the materials used to make them. Sculptures must, for example, be stable, which requires an understanding of the properties of mass, weight distribution, and stress. Paintingsmust have rigid stretchers so that the canvas will be taut, and the paint must not deteriorate, crack, or discolor. These are problems that must be overcome by the artist because they tend to intrude upon his or her conception of the work. For example, in the early Italian Renaissance, bronze statues of horses with a raised foreleg usually had a cannonball under that hoof. This was done because the cannonball was needed to support the weight of the leg. In other words, the demands of the laws of physics, not the sculptor's aesthetic intentions, placed the ball there. That this device was a necessary structural compromise is clear from the fact that the cannonball quickly disappeared when sculptors learned how to strengthen the internal structure of a statue with iron braces (iron being much stronger than bronze).
6. Why does the author discuss the bronze statues of horses created by artists in the early Italian Renaissance?
○ To provide an example of a problem related to the
laws of physics that a fine artist must overcome
○ To argue that fine artists are unconcerned with the
laws of physics
○ To contrast the relative sophistication of modern
artists in solving problems related to the laws of
physics
○ To note an exceptional piece of art constructed
without the aid of technology
