2017届广西来宾市高考英语一轮复习阅读理解专项练习：66（含解析）_高考复习指南

2017届广西来宾市高考英语一轮复习阅读理解专项练习：66（含解析）

　　【解析】选A。推理判断题。文章第一段提到狗和人们一同跨过the Bering Land Bridge, 第二、三、四、五段研究狗的DNA“to conclude that today’s domestic dog originated in Asia”, “Researchers have agreed that today’s dog is the result of the domestication of wolves thousands of years ago”, 所以文章中心是谈论北美的狗的起源。

　　A,B,C或D四个选项中，选出最佳选项。

　　Have you ever noticed the colour of the water in a river or stream after a heavy rainfall?What do you think caused this change in colour?It is soil that has been washed into the river from the riverbank or from the nearby fields. Components of Soil

　　Soil is made up of a number of layers(层),each having its own distinctive colour and texture. The upper layer is know as the litter. It acts like a blanket,limiting temperature changes and reducing water loss. The topsoil layer is made up of small particles of rock mixed with rotten plant and animal matter called humus(腐殖质),which is black and gives the topsoil its dark colour. This layer is usually rich in nutrients,oxygen,and water. Below the topsoil is the subsoil,a layer that contains more stones mixed with only small amounts of organic matter. This layer is lighter in colour because of the lack of humus. Beneath the soil lies a layer of bedrock.

　　Soil forms from the bottom up. Over time bedrock is attacked by rain,wind,frost,and snow. It is gradually broken down into smaller particles in a process called weathering. Plants begin to grow,and rotten materials enrich the topsoil. Most of the soil in Eastern Canada,for example,was formed from weathered rock that was exposed when the ice disappeared 12,000 years ago. Water Beneath the Soil