A warm welcome ______ to the American guests at the airport tomorrow morning.
A. is given B. has been given C. is going to give D. will be given
科目：高中英语 来源： 题型：053
Destructive insects in larger numbers are finding Alaska forests to be a comfortable home and climate change could be the wel-come mat.
Warmer winters kill fewer insects. Lon-ger, warmer summers let insects complete a life cycle and reproduce in one year instead of two. Warm winters also can damage trees and make them less able to stop insect attacks by changing the nature of snow. Instead of light snow formed at extremely cold tempera-tures, warm winters produce wet, heavy snow more likely to break the tops of spruce trees because they are not well adapted to handling big, heavy, wet snow loads.
Since 1980, spruce bark (树皮) beetles have killed mature white spruce trees on 4. 4 million acres. For lack of two cold winters on end, the numbers of the beetles there blew up while the resistance (抵抗力) of the trees was down at the same time everywhere. Most of the mature trees have been killed in some whole region of the state.
Spruce bark beetles bore into (蛀穿)trunks and feed on the live cambium layer, a thin part of tissue between bark and wood. Trees re-sist beetles with pitch, made up of hydrocarbons including up to 17 forms of terpene (松稀). The rates of those terpenes are a signal of the health of the tree. When a tree is injured, terpene rates go off in one direction.
Using complex chemical receptors (感受 器), spruce bark beetles discover differences in terpenes. Injured trees offer less resistance.
They smell the tree. If the tree's healthy,they try to avoid it Why? If they start to bore into a healthy tree, it's got a lot of pitch, and the pitch is under high pressure. It's boring in and the pitch is pushing it back out.
(1) What would be the best title for the text?
[ ]
A．The Destruction of Forests in Alaska
B．Warm Winters and Its Bad Effects
C．The Way of Spruce Trees' Living in Alaska
D．Destructive Insects on Rise in Alaska
(2) According to the text, how do warm win-ters reduce the trees' ability to resist in-sect attacks?
[ ]
A．By changing the nature of snow.
B．By offering too much water to trees.
C．By making the weather drier.
D．By increasing the insects' growth speed.
(3) The third paragraph mainly tells________.
[ ]
A．winters are warmer and warmer
B．there are more and more beetles
C．the situation of trees is much worse
D．mature trees are easy to be attacked
查看答案和解析>>
湖北省互联网违法和不良信息举报平台 | 网上有害信息举报专区 | 电信诈骗举报专区 | 涉历史虚无主义有害信息举报专区 | 涉企侵权举报专区
违法和不良信息举报电话：027-86699610 举报邮箱：58377363@163.com
