2017届高考英语一轮复习跟踪检测：必修4 Module 6 Unexplained Mysteries of the Natural World（外研版）_高考复习指南

2017届高考英语一轮复习跟踪检测：必修4 Module 6 Unexplained Mysteries of the Natural World（外研版）

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　　(2016·河北省高考适应性考试)Visitors to the dry, hot Sonoran Desert of the southern Arizona and northern Mexico are amazed at the manyarmed giants. They are the saguaro cacti (树形仙人掌), a giant which gives the landscape its __1__ appearance. In the dry desert the saguaro cacti can live for more than 200 years, grow to a __2__ of 60 feet, and have as many as 50 arms.

　　More __3__， the saguaro cacti still persist despite the unbearable desert climate. Those that have grown to old age have __4__ droughts, freezes, flash floods, and bush fires as well as the __5__ caused by groups of rats that eat their seedlings (秧苗). Like all other desert __6__， these leafless giants can store water for use during the desert's long dry seasons by __7__ water through their long roots.

　　Naturally, the great saguaro cacti are a(n) __8__ part of the desert life. Actually the giants may be __9__ to many animals, including woodpeckers, owls, doves, bats and insects. In addition, after a saguaro __10__ the age of 50 or so, coldresistant flowers __11__ at the top of the plants once a year. These flowers __12__ birds, bats and bees, which come for the honey and for the tasty flowers with their black seeds.

　　__13__ the splendid saguaros are plentiful in the Southwest, they are unfortunately __14__. These giant cacti have great value in landscape gardening, and the thieves can earn thousands of dollars by uprooting and __15__ them to nurseries (苗圃). To protect these southwestern __16__， agents for the Arizona Department of Agriculture go around and __17__ the desert. It's a most important job though a hard one. But without the saguaro cacti, many desert animals would suffer a lack of __18__ and loss of nesting sites. The Southwest, too, would __19__ something of unique importance, since these desert giants have become a __20__ of the dry region.