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
40
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
"Nothingraisesmorefearinarepressivegovernmentthanchallengestothe
【B1】[br]【B5】[audioFiles]audio_eufm_j10_007(20082)[/audioFiles]less
Therearemanycountriesaroundtheworldadoptingtheprincipleofsustainable
舞蹈的主题与全人类共同的()相吻合才能被世界接受。A.审美标准 B.兴趣喜好
A.哌拉西林 B.头孢噻肟钠 C.舒巴坦 D.亚胺培南 E.头孢克洛属于
虽然已经有人指出纯电动车的电池生产和回收处理过程仍然很不环保,但对消费者个人而言
按照《中华人民共和国担保法》的规定,不得作为保证人的有()。A.不从事经营活动
通过对我国工业两化融合现状调查,成熟度(应用)下设三类二级指标,其中不包括()。
已知某投资项目的净现值为800万元,原始投资额的现值为700万元,则该项目现值指
下列占用耕地的情形中,减按每平方米2元的税额征收耕地占用税的有()。A.停
最新回复
(
0
)