（1）How many American rivers are seriously polluted？
A.One-sixth of them.
B.One-third of them.
C.Half of them.
（2）When did Susan start the work of cleaning the river？
A.A few weeks ago.
B.Last August.
C.Three years ago.
（3）What did the students find when they came to the river this year？
A.The river had become so clean that a lot of water-birds came back.
B.The river was much cleaner and they had to search for rubbish.
C.There was no garbage left to clean up.
（4）What was the expected reaction of the local people into the river？
A.Most of them would keep on throwing rubbish into the river.
B.They would become more aware of the pollution problem.
C.They would join the students in changing the situation.