The tree people in the Lord of the Rings--the Ents--can get around by walking. But for real trees, it's harder to uproot. Because they're literally rooted into the ground, they are unable to leave and go 26 .
When a tree first starts growing in a certain area, it's likely that the 27 envelope—the temperature, humidity, rainfall patterns and so on--suits it. Otherwise, it would be unable to grow from a seedling. But as it 28, these conditions may change and the area around it may no longer be suitable for its 29 .
When that happens, many trees like walnuts, oaks and pines, rely 30 on so-called "scatter hoarders," such as birds, to move their seeds to new localities. Many birds like to store food for the winter, which they 31 retrieve.when the birds forget to retrieve their food--and they do sometimes--a seedling has a chance to grow. The bird Clark's nutcracker, for example, hides up to 100,000 seeds per year, up to 30 kilometers away from the seed source, and has a very close symbiotic (共生的) relationship with several pine species, most 32 the whitebark pine.
As trees outgrow their ideal 33 in the face of climate change, these flying ecosystem engineers could be a big help in 34 trees. It's a solution for us--getting birds to do the work is cheap and effective--and it could give 35 oaks and pines the option to truly "make like a tree and leave. "
A. ages
B. breathing
C. climatic
D. elsewhere
E. exclusively
F. forever
G. fruitful
H. habitats
I. legacy
J. notably
K. offspring
L. replanting
M. subsequently
N. vulnerable
O. withdraws
答案解析：
根据前文 Because they're literally rooted into the ground, they are unable to leave and go...” (因为它们真正地扎根于地，所以无法离开和去...)，可知这里需要一个表示去别处”的副词。选项 D. elsewhere” (在别处) 符合语境。所以选 D。
根据空格后的破折号和 the temperature, humidity, rainfall patterns and so on” (温度、湿度、降雨模式等等)，可知这些是对空格处名词的解释说明，它们共同构成了气候”环境。选项 C. climatic” (气候的) 与 envelope” (包络，此处引申为环境) 搭配，构成 climatic envelope” (气候环境)，是生态学常用术语，符合语境。所以选 C。
根据前文 When a tree first starts growing...” 和后文 But as it... these conditions may change...” (但是随着它...，这些条件可能会改变)，可知此处需要一个表示随着树木成长/变老”的动词。选项 A. ages” (变老，成熟) 符合语境。所以选 A。
根据前文 the area around it may no longer be suitable for its...” (它周围的地区可能不再适合它的...)，可知这里需要一个名词，指代树木的生存繁衍。当环境变化，地区不再适合其生长，自然也就不再适合其繁衍后代”。选项 K. offspring” (后代，子孙) 符合语境。所以选 K。
根据空格后的 on so-called "scatter hoarders," such as birds” (在所谓的分散储藏者，比如鸟类身上)，可知这里需要一个副词来修饰 rely on”，表示依赖”的程度。后文详细描述了鸟类对树木种子传播的关键作用，说明树木是完全”或专门”依赖它们的。选项 E. exclusively” (专门地，唯一地) 符合语境。所以选 E。
根据空格前的 which they... retrieve” (它们...取回)，可知这里需要一个副词，描述鸟类取回食物的时间顺序。鸟类先储存食物，之后”再取回。选项 M. subsequently” (随后，后来) 符合语境。所以选 M。
根据空格前的 a very close symbiotic relationship with several pine species, most... the whitebark pine” (与几种松树有非常紧密的共生关系，尤其是...白皮松)，可知这里需要一个副词，用于举例说明，强调白皮松是其中最典型的例子。选项 J. notably” (尤其，特别地) 符合语境。所以选 J。
根据空格前的 As trees outgrow their ideal...” (随着树木不再适应它们理想的...)，可知这里需要一个名词，指代树木生活的场所或环境。选项 H. habitats” (栖息地) 符合语境。所以选 H。
根据前文 these flying ecosystem engineers could be a big help in... trees” (这些会飞的生态系统工程师可以在...树木方面提供巨大帮助)，可知这里需要一个动名词，表示鸟类对树木的帮助行为。结合全文主题，鸟类帮助树木将种子传播到新的地方，这实际上是一种重新种植”或帮助其重新定居”的过程。选项 L. replanting” (重新种植) 符合语境。所以选 L。
根据空格后的 oaks and pines the option to truly "make like a tree and leave."” (给橡树和松树真正像树一样离开”的机会)，可知这里需要一个形容词，描述这些树木的处境。前文提到，在气候变化面前，树木无法自己移动，处境危险。鸟类的帮助给了这些脆弱的”树木一线生机。选项 N. vulnerable” (脆弱的，易受伤害的) 符合语境。所以选 N。
