[解析]
(1)细节理解题。根据第二段中的Usually,it crosses the Atlantic Ocean as part of a natural cycle (圈) that helps develop farmland in Central and South America. (通常,它作为自然循环的一部分穿越大西洋,这有助于开发中美洲和南美洲的农田。)可知,通常情况下,撒哈拉空气层对农田很友好,故选A。
(2)推理判断题。根据第三段中的In fact,it has a special name,calima.It is so large that it can be seen from space. (这种风暴在西班牙并不罕见。事实上,它有一个特殊的名字,卡利马。它如此之大,以至于可以从太空中看到。)可知,西班牙的calima是巨大而且著名的,故选C。
(3)词义猜测题。根据划线单词的上一句The dust cloud continued to move north and west,hitting both France and the United Kingdom. (尘云继续向北和向西移动,袭击了法国和英国。预计灰尘将继续传播,可能会一直向北到丹麦。)可知划线单词所在句子The dust is expected to keep stalking,possibly as far north as Denmark.的意思是:预计灰尘将继续跟踪,可能会一直向北到丹麦。因此第四段中带下划线单词的意思是"传播",结合选项A.Rising上升;B.Spreading传播;C.Getting weak变弱;D.Becoming different变得不同。故选B。
(4)文章出处题。通读全文可知本文主要介绍了每年撒哈拉沙漠都会升起一大片被称为撒哈拉空气层的尘土,它是自然循环的一部分。同时介绍了撒哈拉空气层所经之处对天气变化的影响。尤其第二段中的Every year,a large cloud of dust rises from the Sahara Desert.It's called the Saharan Air Layer.Usually,it crosses the Atlantic Ocean as part of a natural cycle (圈)that helps develop farmland in Central and South America. (每年,撒哈拉沙漠都会升起一大片尘土。它被称为撒哈拉空气层。通常,它作为自然循环的一部分穿越大西洋这有助于开发中美洲和南美洲的农田。)可知,这篇文章可以出现在报纸的自然部分。故选D。