题目内容：
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?
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