A new analysis of satellite-based data has given precisely the rate 21 which the country is losing size as it pushes northward against the Himalayas.
答案：(D) at
the rate at which 是固定結構：原句為 the country is losing size at a certain rate，介系詞 at 隨關係代名詞一起前移，成為 the rate at which…；by／in／of 都不是 rate 慣用的介系詞。
答對率 15%。
看到 which 你就自動進入「關係代名詞」模式，滿腦子想的是該用 that 還是能不能省略，完全沒意識到要填的是「介系詞」，而且它由前面的名詞 rate 決定。
at 的核心是標出一個點——空間的點（at the corner）、時間的點（at seven）、瞬間的反應（at first sight 一見鍾情）。凡是把某個量看成刻度上的一個定點，一律用 at：at a rate of 2 cm a year、at a speed of 60 km／h、at a temperature of 100°C、at the age of 18。速率是刻度上的一點，所以配 at。
把關係子句還原成獨立句子就看得出來：The country is losing size 「at」 a certain rate. → the rate 「at which」…。國中學過的 the house 「in」 which I live（＝the house I live 「in」）是同一招。
at a rate of（以…的速率）、the rate at which SV（…的速率）、at first sight（一見鍾情、乍看之下）、the way in which SV（…的方式）、the extent to which SV（…的程度）。
India is shrinking. A new analysis of satellite-based data has given precisely the rate 21 which the country is losing size as it pushes northward against the Himalayas. According to the analysis, the 22 between India's southern and northern tips shrinks by 2 cm every year. As India's size decreases, the thickness of the Himalayas increases. 23 the shrinking continues, India will disappear in 200 million years. There would only be a vast mountain range along the southern coast of China.
The Indian plate's 24 movement is not new. However, this cannot be treated as a trivial finding in science. A movement of 25 a few millimeters (mm) of the earth's crust is a sign of possible earthquakes. Such dangers are now obvious in India, where the movement of the plate continues.