首页
登录
职称英语
Canals are watercourses constructed to improve and extend natural waterways
Canals are watercourses constructed to improve and extend natural waterways
游客
2024-10-31
30
管理
问题
Canals are watercourses constructed to improve and extend natural waterways. They are generally built to facilitate transportation, but from the beginning they have been used for many additional purposes including draining swamps, irrigating land for cultivation, and promoting economic development.
Canals are often classified by the size of vessel they can accommodate. Some small local canals, which are able to float only 100 to 300 ton boats or small rafts of timber, may be only 3 feet deep. Major barge canals generally range from 6 to 9 feet in depth, and some are as much as 10 or 12 feet deep. These canals can carry 1,350 to 2,000 ton craft. Ship canals are 25 feet or more deep and are capable of accommodating large vessels in the seagoing class.
Canals may also be classified as either water level or lock canals. Water level canals do not vary in height along their courses. The best known of these is the Suez Canal, which is at sea level. Lock canals, which include most modem waterways, contain locks, or special devices for raising and lowering boats along their courses by changing the depth of the water. Each lock is a stretch of water enclosed by gates at each end. After a boat enters the lock, water is let or drained out until it reaches approximately the same level as the water ahead. [br] What does the passage mainly discuss?
选项
A、How canals are constructed.
B、Common types of canal boats and barges.
C、The world’ s largest canals.
D、How canals are used and classified.
答案
D
解析
通读全文不难发现,每段第一句即为段落主题句,第一段讲什么是canal,第二、三段讲的canal不同分类及其作用,因而本题应该选D。
转载请注明原文地址:https://tihaiku.com/zcyy/3825278.html
相关试题推荐
Bycuttingdowntreeswe______thenaturalhabitatofbirdsandanimals.A、damag
AsIregardit,youcanwidenthe______oftheseimprovementsthroughyouracti
GermanhavelawmakersvotedtoextendandexpandtheroleofGermanpeacekeepers
GermanhavelawmakersvotedtoextendandexpandtheroleofGermanpeacekeepers
Canalsarewatercoursesconstructedtoimproveandextendnaturalwaterways
Canalsarewatercoursesconstructedtoimproveandextendnaturalwaterways
Canalsarewatercoursesconstructedtoimproveandextendnaturalwaterways
Ourape-menforefathershadnoobviousnaturalweaponsinthestruggleforsu
Ourape-menforefathershadnoobviousnaturalweaponsinthestruggleforsu
Ourape-menforefathershadnoobviousnaturalweaponsinthestruggleforsu
随机试题
A.divisionB.sufficientC.constantD.depthsE.exteriorF.whereasG.stable
Adetectivestoryaffectsmequite(differ)______fromtheotherkindsofstori
HowtoSurviveaLayoffYou’velostyourjob,butit
患者,女,17岁,颏部外形发育不良,口唇闭合时口腔周围肌肉呈现紧张,面下1/3高
下列关于生物碱叙述错误的是A.酰胺生物碱几乎不显碱性B.脂肪胺显中等碱性C.季铵
制定进度计划的方法有横道图法和()。A、水平进度计划表 B、网络图法
在计算经营者的效益年薪时。()模式认为经营者的效益收入就是其经营的风险收入。A
真核细胞呼吸链位于A.线粒体外膜 B.线粒体内膜 C.细胞膜 D.核膜
水工建筑物中高桩码头,代替后方抛石棱体碎石反滤层的土工织物应采用()。A.土工膜
根据《建设工程施工合同(示范文本)》,对已缴纳履约保证金的承包人,其提交的竣工结
最新回复
(
0
)