Read the passage: "Zebra mussels, small freshwater shellfish native to Eastern Europe, were first found in the Great Lakes in the late 1980s, probably carried there in water released from cargo ships. Each mussel filters about a liter of water a day, removing tiny floating algae. In infested lakes the water has become noticeably clearer. Clear water might seem like an improvement, but the algae the mussels remove are the main food of small animals that young fish depend on. Meanwhile, sunlight now reaches deeper, allowing weeds to grow on the lake floor. Mussels also attach in dense layers to water-intake pipes, and power plants and cities spend millions of dollars each year to remove them." Which conclusion is best supported by the passage?
Show answer & explanation
Answer: B
Zebra mussels will soon disappear because they eat all the algae.: The passage makes no prediction about the mussels dying out.
Clearer water does not always mean a lake ecosystem is healthier.: Correct. The author contrasts clearer water with the loss of food for young fish and the growth of lake-floor weeds, implying clarity can hide harm.
Cargo ships no longer carry living organisms between countries.: The passage only says mussels probably arrived in ship water; it says nothing about current shipping.
Power plants caused the spread of zebra mussels in the Great Lakes.: Power plants are harmed by mussels clogging pipes; they are not described as the cause.
An inference must be supported by the passage's evidence; reject choices that predict or add facts the author never gives.