II．完形填空。从A、B、C、D四个选项中，选择一个正确答案，并填在答题纸相应的位置上。错选、多选或未选均无分。（本大题共15小题，每小题1分，共15分）
Bridge is a structure used by people and vehicles to cross areas that are obstacles to travel. Without bridges, people would need 16 to cross waterways and would have to travel around such obstacles 17 canyons and valleys.
Bridges range 18 from a few feet or meters to several miles or kilometers. A bridge must be strong enough to support its own weight 19 the weight of the people and vehicles that use it. It must also 20 natural occurrences, including earthquakes, strong winds, and changes in temperature.
Most bridges are held up by at least two supports set in the ground. The 21 between two adjacent supports is called a span of a bridge. The supports at each 22 of the bridge are called abutments (桥墩), and the supports that 23 between the two abutments are called piers. Most short bridges are supported only by abutments and are known as 24 -span bridges. Bridges that have one or more piers 25 the abutments are called multi-span bridges. Most long bridges are multi-span bridges. The main span is the longest span of a multi-span bridge.
Suspension bridges (吊桥) are perhaps the most 26 type of bridge because of their long main span and especially attractive 27 . These bridges have a roadway that hangs from steel cables that are supported by two high towers. Suspension bridges are used to 28 great distances. They are also used to cross deep water or steep canyons, and in other places 29 the construction of piers is especially difficult and 30 . These bridges require only two piers, each of which supports a tower.
16. A. buses B. planes C. trains D. boats
17. A. like B. as C. with D. to
18. A. in height B. in depth C. in length D. in width
19. A. as well as B. by means of C. except for D. according to
20. A. prevent B. resist C. beat D. fight
21. A. space B. extent C. distance D. stretch
22. A. end B. side C. way D. part
23. A. run B. remain C. stay D. stand
24. A. sole B. unique C. single D. simple
25. A. in proportion to B. in addition to C. in place of D. in front of
26. A. impressive B. expressive C. productive D. constructive
27. A. existence B. appearance C. quality D. ability
28. A. measure B. move C. extend D. span
29. A. while B. when C. where D. which
30. A. profitable B. practical C. necessary D. expensive
