Today, most countries in the world have canals.Many countries have built canals near the coast, and parallel 1 the coast.Even in the twentieth century， goods can be moved more cheaply by boat than by any other 2 of transport.These 3 make it possible for boats to travel 4 ports along the coast without being 5 to the dangers of the open.Some canals, such as the Suez and the Panama, save ships weeks of time by making their 6 a thousand miles shorter.Other canals permit boats to reach cities that are not 7 on the coast, still other canals 8 landsswheresthere is too much water， help to 9 fields wherethere is not enough water, and 10 water power for factories and mills.The size of a canal 11 on the kind of boats going through it.The canal must be wide enough to permit two of the largest boats using it to 12 each other easily.It must be deep enough to leave about two feet of water 13 the keel of the largest boat using the canal.When the planet Mars was first 14 through a telescope, people saw that the round disk of the planet was criss-crossed by a 15 of strange blue-green lines.These were called canals 16 they looked the same as canals on earth 17 are viewed from an airplane.However, scientists are now 18 that the Martian phenomena are really not canals.The photographs 19 from space-ships have helped us to 20 the truth about the Martia canals .
1.A.off B.with C.to D.by
2.A.way B.means C.method D.approach
3.A.waterways B.waterfronts C.channels D.paths
4.A.among B.between C.in D.to
5.A.revealed B.exposed C.opened D.shown
6.A.trip B.journey C.voyage D.route
7.A.lain B.stationed C.set D.located
8.A.escape B.drain C.dry D.leak
9.A.water B.wet C.soak D.irrigate
10.A.furnish B.afford C.offer D.give
11.A.focuses B.bases C.depends D.takes
12.A.cross B.pass C.move D.advance
13.A.down B.below C.beneath D.off
14.A.studied B.researched C.surveyed D.observed
15.A.few B.number C.deal D.supply
16.A.although B.because C.so D.if
17.A.that B.where C.when D.as
18.A.exact B.definite C.certain D.decisive
19.A.held B.taken C.got D.developed
20.A.find B.expose C.uncover D.discover
答案与解析：
1.C
parallel to 与 平行 ，固定搭配。
2.B
means of transport 交通工具 ，固定搭配。
3.A
waterways 水道 ;waterfronts指城市的滨水区;channels指海峡;paths指小路。
4.B
between指在两个港口间航行。among指三个或三个以上。
5.B
expose 使暴露、面临 后接to;reveal 显示 ;show 展示 ;open意为打开。本句意为暴露在危险面前。
6.C
voyage特指水上航行，其他选项均与水无关。
7.D
locate 位于 ;stationed 住扎于 ;set 放置于 。lie则不用被动式。
8.B
drain指排掉(过多的水);其他选项不符合题意。
9.D
irrigate指灌溉;soak浸泡，及其他选项不符合题意。
10.A
与介词for搭配的只有furnish.
11.C
depend on 取决于 ;base on 把 基于 ;take on 承担 ;focus on为集中注意力。
12.B
本句的意思是 运河必须有能够允许两条最大的船通过的宽度 。只有pass 通过 符合句意。Cross 穿过、横跨 与句意不符。
13.C
beneath指在 以下，表示位置;down指向下，表方向;below用于抽象概念;off表示距离。
14.D
表示 用 观测 ，要用observe;study、research指系统研究;survey指调查、检查。
15.B
a few of是一些的意思，修饰可数名词;a deal of不能修饰可数名词;a number of指大量的;无a supply of的用法。
16.B
根据句意，这里要用表原因的连词来引导一个状语从句。
17.A
此处用that指代canals.
18.C
在四个选项中，只有certain有确信的意思。exact和definite的主语应为事物，decisive不符合句意。
19.B
take photographs是固定搭配，意为拍照。
20.D
discover指发现抽象的事物;find指发现实物;expose指暴露;uncover指揭开。后两词不符合句意。