单选题 Water, water everywhere.
It lasted almost two months, but in August it ended. It left 45 people dead and $10 billion worth of damage in nine states of the USA. It was quite a big Mississippi flood ever recorded.
In St. Louis, Missouri, 9,000 people were forced to leave their homes while the city was in danger. St. Louis is just downriver from the points where the Missouri and Illinois Rivers flow into the Mississippi. All the three rivers were flooding. But the city escaped the worst when levees broke upriver. A levee is built of river sand and clay.
Eleven miles of flood walls were built in the late 1960s. The walls are 18 inches thick and 5 to 22 feet high. They were designed to protect against a 52-foot flood. In St. Louis, water almost reached the top of flood walls. It measured 49.4 feet.

单选题 The flood referred to in the passage ______.
【正确答案】 C
【答案解析】[精解] 题干问：“文章中提到的洪水情况是什么样?”文章说这次洪水是有记录以来很大的一次，而不是历史上最大的一次，所以答案A不正确。洪水发生在美国的9个州，所以选项B说得不全面。美国共有50个州，9个州的数量小于美国州总数的20%，所以选项C是正确的。这么大的洪水是有记录以来的第一次，所以说它被记录了几次是错误的，D错误。
单选题 The highest flood referred to in the passage was about ______.
【正确答案】 C
【答案解析】[精解] 题干问：“文章中提到的最高的洪水大约有多高?”文章最后一句说“测量有49.4英尺。”所以答案C“几乎50英尺高”是正确的。
单选题 The meaning of the words "But the city escaped the worst" is that ______.
【正确答案】 B
【答案解析】[精解] 题干问：“But the city escaped the worst的意思是什么?”文章是说通过预防和及时疏散群众，这个城市避免了最坏的情况。所以答案B符合题意。