There are many brave and talented people who work in different branches （分科，分支） of science．Extreme （另类的）scientists are people who work in very difficult and dangerous places．They don't work in a（1） 　　all the time like other scientists do．Instead，they search（2） 　　information that can only be gathered through firsthand experiences．These scientists have to explore deep，dark caves，swim with sharks or act as swan（天鹅） mothers．The number of great white sharks in the world（3） 　　smaller now． They are one of（4） 　　animals on Earth．

Scientists need to find out how many sharks（5） 　　now．Sometimes scientists have to get very close to a shark．The easiest and（6） 　　way to do this is from inside a shark cage（笼子）．（7） 　　，sometimes sharks attack（袭击，攻击） the cage．They shake it，and bend the bars with their sharp（8） 　　．The trumpeter swan is the largest swan in the world，but it （9） 　　until it nearly became endangered birds． Because of this，parents swans （10） 　　younger swans to migrate before．

Scientists have to teach the younger swans how to do it．They teach the swans to follow a plane which looks like a lead swan． Extreme scientists are always trying to discover something new．

（1）A．hospital	B．factory	C．lab	D．hotel
（2）A．for	B．to	C．of	D．at
（3）A．get	B．is getting	C．was getting	D．got
（4）A．dangerous	B．more dangerous	C．most dangerous	D．the most dangerous
（5）A．there were	B．are there	C．there are	D．were there
（6）A．safest	B．closest	C．farther	D．faster
（7）A．Lovely	B．Unlovely	C．Luckily	D．Unluckily
（8）A．teeth	B．tooth	C．eye	D．eyes
（9）A．kills	B．killed	C．was killed	D．is killed
（10）A．won't teach	B．have never taught	C．wouldn't teach	D．don't teach