A newly published study, however, revealed that rising temperatures are posing an 27 threat to the last tropical glaciers in Indonesia’s Papua region.
答案：(C) immediate
語意「氣溫上升對最後的熱帶冰川構成『立即』的威脅」，immediate（立即的）符合這種緊迫性；occasional（偶爾的）、elaborate（精心製作的）、offensive（冒犯的）都不合。
immediate 你最熟的是「立刻的」，多半配時間用（immediately 馬上）。放進 an ___ threat 裡，你可能覺得威脅怎麼會「立刻」，於是改挑別的。an immediate threat 是固定說法，指迫在眉睫、不能再拖的威脅，強調的是急迫性。
後面兩句把急迫感寫得很滿：The ice sheets... are thinning over five times as quickly compared to a few years ago（融化速度是幾年前的五倍以上）、will completely disappear within a decade（十年內就會完全消失）。「五倍速」加上「十年內消失」，這就是急迫。
occasional（偶爾的）與「持續加速融化」矛盾；elaborate（精心製作的）用來形容計畫或設計，威脅不會「精心製作」；offensive（冒犯的；攻擊性的）用在言語或軍事行動上，氣候變遷並不是刻意冒犯誰。
an immediate threat（迫在眉睫的威脅）、pose a threat to（對……構成威脅）、take immediate action（立刻採取行動）、immediate family（直系親屬）、an elaborate plan（精心設計的計畫）、ice sheet（冰層、冰原）。
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.