One weekend in May 2015，over 48centimeters of rain fell in Houston，Texas，USA．Soon the city was covered with water．The rising water rushed into the cars on the roads．There were 16deaths that weekend．
Changing Weather
The weather is changing．Over the last few years，heavy rains have caused floods in Brazil，Pakistan，and Thailand．Droughts（干旱） have struck Russia and Australia．Heat waves have killed thousands in Europe．There are more different kinds of terrible wild weather all over the world．In 2011alone，the bad weather caused the world to lose 150billion dollars．
Warmer and Wetter
As more wild weather events happen，a worried world is beginning to ask questions like：What is going on with the weather？And why？Many also want to know：Is this natural，or are we to blame （责怪）？
The answer seems to be：a little of both．Wild weather is natural． This global （全球的） warming makes heat waves more likely to happen．The higher temperatures also cause more water to enter the air．This causes much more rain．Some scientists also believe global warming makes some storms stronger．
This means we're likely to see more wild weather．"But we don't have to just stand there and take it，"says Scientist Michael Oppenheimer．He and other scientists say we need to stop the Earth from getting warmer．We also need to be prepared，to do things that will help save lives．
38．What is the purpose of the second paragraph？___
A．To explain why the weather is changing．B．To guess how the weather will change．
C．To give examples of wild weather events．D．To describe the weather events in 2011．
39．Which of the following can be put in the blank in Paragraph 4？___
A．And wild weather happens more and more．
B．And nature also influences human activity．
C．But most scientists agree human activity has made the Earth warmer．
D．But humans have already paid enough attention to the wild weather．