四六级考试

根据网考网考试中心的统计分析，以下试题在2015-11-15日四六级考试六级习题练习中，答错率较高，为：43%
【单选题】T[ornadoes,whirlwinds,and watersprouts are rotating funnel cloud air masses of small diameter.They are differentiated by the intensity of their rotation and by
the surfaces that they traverse.Though tornadoes and whirlwinds both travel over land masses,whirlwinds are atmospheric systems smaller than tornadoes.Watersprouts are tornadoes that form or pass over a water surface.A tornado is a powerful vortex or “twister” whose rotational speeds are estimated to be near 300 miles per hour.The first visible indication of tornado development is usually a funnel cloud.As this funnel dips earthward,it becomes darker because of the debris
that is forced into its intensifying vortex.Some tornadoes give no visible warning until their destruction strikes the unsuspecting victim.Tornadoes often occur in groups,and several twisters sometimes descend from the same cloud base.The forward speed of a tornado is normally 30 to 40 miles per hour.In the short time that it takes to pass,a tornado can cause fantastic destruction.There have been cases reported in which blades of straw were embeded in fence posts.
31. How are tornadoes distinguished from whirlwinds?
A.Whirlwinds rotate in a different direction than tornadoes do.
B.Tonadoes travel over land and whirlwinds over water.
C.Tonadoes are larger than whirlwinds.
D.Only tornadoes are funnelshaped. 
32. Why do tornadoes appear to be dark?
A.They occur only at night.
B.They are funnel-shaped.
C.They pick up debris from the ground.
D.They are water-laden. 
33. According to the passage,which of the following behaviors is frequently
characteristic of funnel clouds?
A.Descending from different cloud bases.
B.Occurring in isolated areas.
C.Lasting a long time.
D.Occurring in groups. 
34. According to the passage,some tornadoes take people unaware because they__.
A.produce a sound similar to thunder.
B.cannot be seen until it is too late.
C.look so much like other clouds.
D.carry so many large pieces of debris. 
35. The author refers to straw embeded in fence posts in order to show __.
A.where tornadoes occur.
B.who makes reports about tornadoes.
C.when tornadoes take form.
D.how tornadoes affect physical objects. 

网考网参考答案：C、C、D、B、D，答错率：43%
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