20．
One city in America that has got the most new residents（居民）is Las Vegas．
People move to Las Vegas for many reasons．First，it is easy to find a job in Las Vegas．Las Vegas is famous for tourism（旅游业），so there are many service jobs．Second，many people like the weather there．Even though it's very hot in summer，the other seasons are beautiful．Third，housing is not very expensive to people moving from other cities．Also，it is easier to get married in Las Vegas than in any other city in the United States．You can get a marriage license（结婚证）the same day you decide to get it．
However，Las Vegas also has problems．Because it is in the desert，there is not enough water．Even though water is expensive，residents aren't careful in using it．Next，Las Vegas has serious air pollution．There are some high mountains around Las Vegas．The mountains keep the pollution from going out．Sometimes people couldn't exercise outdoors．
46．The second paragraph mainly tells usB．
A．how people live in Las Vegas
B．why people move to Las Vegas
C．when people tour in Las Vegas
47．What problems does Las Vegas have？C
①not enough jobs ②not enough water ③serious air pollution
A．①②B．①③C．②③
48．What is NOT mentioned about Las Vegas in the passage？C
A．Housing． B．Weather． C．Population．
49．Which of the following is TRUE according to the passage？A
A．Las Vegas is a popular place for tourists．
B．It is not easy to get married in Las Vegas．
C．People in Las Vegas know how to save water．
50．You may find the passage in a（n）B．
A．science newspaper B．traveling magazine C．environment report．
