Blood is not properly filtered, leaving waste on the blood.
Your answer would be Why are Sea Lampreys a problem in the Great Lakes?
In the text, it explains the answer for this question. For the other three questions, it's asking for a factor of the paragraph rather than the whole thing. The whole paragraph explains the answers for all of the questions, so it's best to ask why are they causing problems.
Answer:
a hygrometer consisting of a wet-bulb and a dry-bulb thermometer, the difference in the two thermometer readings being used to determine atmospheric humidity.
a hygrometer is an instrument for measuring the humidity of the air or a gas.
