题目
From the 1500s to the mid-nineteenth century ,a period known as the Little
Ice Age , tree rings show that the climate in western North America was much
colder than normal. That favored the grass bison eat ,and they decreased .
When a long, widespread drought ended the Little Ice Age in the mid-1800s ,
the grassed _____ and the bison population crashed.
有三个选项
improved
spread
changed
我选的是 spread 答案却是 changed
我的观点因为 bison 爱吃草 , 所以草 decreased
所以当 bison 数量急遽下降导致 grass spread

bison population crashed的原因是因为grasses变少吧？如果grasses spread，bison population反而应该增加才合理。我认为这边的changed隐含的意思就是grasses decreased，有误请指正

因果关系 先讲的是因 草增加的话bison减少说不通

Grassed打错字了吧 我觉得changed应该是指植皮改变 不应对于学术文章的用字有过多推论 这题应该是题本出的？我觉得改的不好 一楼的原文写的比较有逻辑 favored the grasses and they flourished很合理 但题目说favored thegrasses and they decreased 既然气候适合那种草 草怎么又会变少？ 这题硬要选还是会选changed 但是题目不好

楼上因为他打错了 指的是grasses buffaloes not grasses题目纯粹是考原本说flourished然后转折以后你要选相对的