47、How many different forms of communication are mentioned in the passage?
48、根据以下材料回答第 1～4 题：
Passage Four
John Paul Jones was one of the founders of the United States Navy．During the Rev0lution，the colonies were desperate．They needed men to lead their small ships against the British fleet．Jones was more than willing to fight．
John Paul Jones had once been a captain of a British merchant ship．In l 773，his crew mutinied．One member of the crew tried to gain control of the ship．Jones shot the man to death．The mutiny took place near the port of Tobago，an island in the Caribbean．Authorities thers decided to have a trial．This meant certain death for John Paul Jones，since the whole crew would testify against him．One night during a thunderstorm，he escaped from the jail．
He fled to the United States and lived with a family named Jones．His real name was John Paul．He added the name of Jones to his，in honor of the family．He outwitted the British ships that were sent to hunt him down．
When the American Revolution ended he went to serve in the Russian navy．There，he fought the Turks and achieved one of the few major naval victories in the history of Russia．He died in Paris at the age of forty-five．
John Paul Jones is considered both an American and Russian hero，but the English considered him a fugitive．
John Paul Jones won fl major victory for the Russian navy against the ．
49、You can conclude from this passage that Jones was ．
50、The passage is basically a ．
51、“Desperate”means ．
52、根据以下材料回答第 1～4 题：
Passage five
The Northern Pike is a very bad fish．It is a bi9，hungry fish，and swallows little fishsuch as trout and Derch．Many Northern Pikes live in Lake Davis．They are killing all thesmaller fish in the lake．The Northern Pike are a serious threat to the lake because theyeat all the smaller fish．Soon，all other species of fish in the lake will be killed off．This isnot healthy for the environment．
Experts are afraid that the Northern Pick will swim out of Lake Davis through many
smaller rivers that feed into the lake．They could spread all over the country and damagemanv other water environments．If that happens，it would be too late to stop the NorthernPike．
For ten years,officials have been trying to remove the Northern Pike from Lake Davis．They have tried using nets，explosives and poisons．However，the Northern Pick puDulation is stilt doing well in Lake Davis．Many people do not like the idea of using poisonto kill the fish．They worry that the poisons are bad for humans who use the water．Notrace of the poisons has ever been found in local wells，however．
Scientists are going to try the posison again．This time，they will drain the lake before they add the poison to the water．A public hearing will be held to talke about the problem．
Why are some people against the use of poisons to kill Northern Pike?
53、What will scientists do to make sure the poison works this time?
54、What are the experts afraid will happen?
55、Why is it a problem if all the smaller fish species die?
