【单选题】

Several regions in the world are subject {{U}} 21 {{/U}} storms which are so severe that they cause damage on a tremendous scale. The regions are all located on the edges of great oceans. The {{U}} 22 {{/U}} term for such severe storms is “cyclone”(龙卷风). The term “hurricane” is {{U}} 23 {{/U}} for storms that occur in the NorthAtlantic Ocean. Cyclones and hurricanes differ in one curious {{U}} 24 {{/U}} : in a cyclone, the wind circulates in a clockwise direction; in a hurricane, the wind direction is counter-clockwise. {{U}} 25 {{/U}} cyclones and hurricanes have one ominous similarity. {{U}} 26 {{/U}} the damage they cause on land and at sea， they are identical.Australia undergoes a number of cyclones every year along its northern coast, which faces Indonesi

A、The cyclones occur mainly inDecember and January, the summer months in the southern hemisphere.{{U}} 27 {{/U}} theAustralian cyclones don’t cause great damage becauseAustralia’s northern territory has vast empty regions that are virtually unpopulateD、There are {{U}} 28 {{/U}} coastal cities. When a cyclone does move inland from the sea, it usually blows itself out without {{U}} 29 {{/U}} any inhabitated are
A、However, in 1917 the small city of Townville was {{U}} 30 {{/U}} devastated by a cyclone. There was a public outcry about it. People demand an adequate warning system.Ever since then the meteorological bureau has regularly issued alarms in advance of every serious cyclone.
A、fighting
B．colliding
C．striking
D．breaking