The ice sheets, which once spanned 20 square kilometers, are thinning over five times as quickly compared to a few years ago. 28 already shrunk by 85% to a mere 0.5 square kilometers, Papua’s glaciers will completely disappear within a decade, researchers have predicted.
答案：(C) Having
完成式分詞構句 Having already shrunk，表示「已經萎縮了85%」（在主要子句動作之前發生），補充說明前提狀況，帶出主要子句的推論；Have（原形動詞，不能這樣作分詞構句開頭）、Had（過去式，分詞構句應該用Having）、Having been（被動完成分詞，方向不合，這裡是冰川「自己萎縮」是主動語態）都不合。
句首要填一個字接 already shrunk，你可能直覺想成「這是完成式，那就用 Have 或 Had」。但關鍵在位置：句子開頭如果是分詞構句，就不能用有時態的動詞。 Have 和 Had 都是有時態的形式，放句首會讓整句出現兩個主要動詞（後面已經有 Papua's glaciers will disappear）。分詞構句要用 -ing 形式，而完成式的分詞就是 Having ＋ 過去分詞。
還原成完整子句最快：Having already shrunk by 85%, Papua's glaciers will completely disappear ＝ Because they have already shrunk by 85%, Papua's glaciers will completely disappear（因為已經萎縮了 85%，巴布亞的冰川將會完全消失）。用 Having 而不是單純的 Shrinking，是因為「萎縮 85%」發生在「將會消失」之前——Having ＋ 過去分詞就是用來標示「這件事更早發生」。
Have 是原形、Had 是過去式，兩者都帶時態，不能當分詞構句的開頭。Having been 是被動的完成分詞，但冰川是自己縮小，不是被誰弄縮的——shrink 在這裡是不及物動詞，沒有動作的施予者，這種用法不會有被動式。判斷主動或被動，問一句「主詞是自己做，還是被別人做」就好。
Having ＋ 過去分詞（分詞構句，表更早發生）、Having finished his homework, he...（做完功課後，他……）、shrink by 85%（萎縮 85%）、shrink from A to B（從 A 縮減到 B）、within a decade（十年之內）、indigenous（原住民的）。
Glaciers are usually associated with colder climates. But some mountain ranges of South America, Africa, and Indonesia are also 26 glaciers and ice sheets. These tropical glaciers serve as a major source of water supply to one-sixth of the world's population.
A newly published study, however, revealed that rising temperatures are posing an 27 threat to the last tropical glaciers in Indonesia's Papua region. The ice sheets, which once spanned 20 square kilometers, are thinning over five times as quickly compared to a few years ago. 28 already shrunk by 85 to a mere 0.5 square kilometers, Papua's glaciers will completely disappear within a decade, researchers have predicted.
The disappearance of the glaciers will also leave a significant 29 impact. For many indigenous Papuans, the ice sheets represent a sacred symbol. "The mountains and valleys are the arms and legs of their god and the glaciers are the head," explained the head researcher. The study warned that Papua's glaciers are only the "first to go" if greenhouse gases are 30 and temperatures continue rising. And this is certainly a serious warning about the depressing fate of other glaciers around the world.