The size of the food they are about to eat is magnified while 27 of their hand remains normal.
答案：(B) that
that 在此代替前面出現過的單數名詞 the size，避免重複：食物的尺寸被放大，而手的尺寸維持不變；this 不用於這種比較替代，some 與 other 都無法代替 the size。
答對率 35%。
that 你大概只想到關係代名詞或「那個」，不知道它可以代替前面出現過的名詞，避免重複。本句完整寫法是 …while the size of their hand remains normal.，第二次的 the size 就用 that 頂替。
單數用 that、複數用 those，後面接 of：The head has a similar shape and size to that of a mammal.（頭部的形狀與大小與哺乳類的相似）。這跟 Do you like it?—Yes, I do. 用 do 代替 like it 是同一件事，只是換成代替名詞。
that of／those of（代替前文出現過的名詞）、the same as that of（與…的相同）、compared with that of（與…的相比）。
Researchers from a university in Japan have developed "diet-glasses" that play tricks with one's perception of food, which could be helpful to people on a diet.
A camera and a viewing system are built 26 these glasses. As the wearer brings the food toward their mouth, the camera captures an image of the food. It replays the image back through the glasses after processing it on an attached computer. The size of the food they are about to eat is magnified while 27 of their hand remains normal. Their brain is 28 tricked into thinking they are eating more than they really are. The study showed that participants who wore the glasses ate 9.3 less than those who did not wear them.
The team has also developed a special device which uses scent bottles and visual trickery to make the wearers of these glasses think that the plain snack they are eating is 29 than it actually is. The device, for instance, can be set to 30 one's favorite flavor. Recent experiments with this device showed that 80 of the participants were fooled by the smell. For example, some participants thought that they were eating a chocolate snack, but in fact they were not.