During recent years, floods and flash floods have caused billions of dollars in damage each year. They are among the most common and widespread of all natural disasters. Even more importantly, they’re No.1 weather-related killer. A flood can happen anywhere along the Mississippi, in New England, even in the desert.

The following are some fascinating facts about floods and flash floods.

A flood（commonly called river flood）is high flow of water from a river or similar body of water, happening over a period of time too long to be considered a flash flood. Flooding is caused in many ways. Winter or spring rains, together with melting snows, can fill rivers too quickly. Heavy rains from hurricanes or other tropical（热带的）systems can also produce river flooding. The Mississippi River Flood of 1993 was caused by repeated heavy rain from thunderstorms over a period of weeks.

Flash floods are quickly-rising floods which are usually the result of heavy rains over a short period of time, often only several hours or even less. They can also be caused by ice jams（冰塞）on rivers related to a winter or spring melting, or occasionally even a dam break. The constant influx（汇集） of water finally caused a great overflow to begin, powerful enough to sweep vehicles away, roll big stones into roadways, uproot trees, level（夷平） buildings, and knock bridges down. The speed of the rising of water is the most frightening.

Do remember: Move to higher ground and stay away from low areas during heavy rain. Stay out of flooded areas. Never allow children especially to play or walk in flowing water. Never drive your car into water of unknown depths.

43. What is the best title for the passage?

A. The power of floods               B. The damage of floods

C. The occurrence of floods           D. The facts about floods

44. The last paragraph is mainly about ______ .          

A. flood safety tips                B. the reasons for floods

C. the waste water systems               D. the swift flood waters

45. According to the passage, people are afraid of _____ most during flash floods.

A. the constant influx of water

B. the sudden occurrence of flash floods

C. the quick rising water

D. the great damage of flash floods

46. According to the passage, flash floods are ______.

A. great floods resulted from heavy rains in a short time

B. floods rising quickly from heavy rains in a short time

C. quickly-rising floods in a long time

D. floods happening over a long time