题目

动物生态学家对林区周边区域进行了4种经济动物的调查，结果如表。根据表中信息，有关叙述错误的是（ ）一二三四五AA1 A3 A5B B2B3B4 CC1C2C3 DD1D2D3 D5A.被调查动物分布最广的是物种DB.A1、A3、A5之间可能存在地理隔离C.第三号区域最能说明遗传多样性D.如选一区域，用标志重捕法调查4种经济动物的种群密度，最好选用第三号区域4、Trees should only be pruned (修剪) when there is a good and clear reason for doing so and , he number of such reasons is small . Pruning involves the cutting away of overgrown and unwanted branches , and the inexperienced gardener can be encouraged by the thought that more damage results from doing it unnecessarily than from leaving the tree to grow in its own way . First , pruning may be done to make sure that trees have  desired shape or size . The object may be to get a tree of the right height , and at the same time to help the growth of small side branches , which will thicken its appearance or give it a special shape . Secondly , pruning may be done to make the tree healthier . You may cut out diseased or dead wood , or branches that are rubbing against each other and thus cause wounds . The health of a tree may be encouraged by removing branches that are blocking up the center and so preventing the free movement of air . One result of pruning is that an open wound is left on the tree and this provides an easy entry for disease , but it is a wound that will heal (愈合) . Often there is a race between the healing and the disease as to whether the tree will live or die , so that there is a period when the tree is at risk . It should be the aim of every gardener to reduce that risk of death as far as possible . It is important to make the area , which has been pruned , smooth and clean , for healing will be slowed down by roughness . You should allow the cut surface to dry for a few hours and then paint it with one of the materials available from garden shops produced especially for this purpose . Pruning is usually done in winter , for then you can see the shape of the tree clearly without interference (妨碍) from the leaves and also it is very unlikely that the cuts you make will bleed . If this does happen , it is , of course , impossible to paint them properly . 68．Why should running be done ?        A．To make the tree grow taller .           B．To improve the shape of the tree .        C．to get rid of the small ranches .         D．To make the small branches thicker . 69．Trees become unhealthy if the gardener         .        A．To help a wound to dry .        B．To cover a rough surface .        C．damages some of the small side branches        D．Allows too many branches to grow in the middle 70．Why is a special material painted on the tree ?        A．To help a wound to dry .          B．to cover a rough surface .        C．To make a wound smooth .     D．To prevent disease entering a wound . 71．A good gardener prunes a tree         .        A．several times throughout the year    B．as quickly as possible        C．occasionally when necessary          D．regularly every winter 72．What was the author’s purpose when writing this passage ?        A．To discuss different methods of pruning .        B．To introduce some common knowledge of pruning .        C．To explain how trees develop disease .        D．To give practical instruction for pruning a tree .