Using traditional classification methods, which of the following sets of organisms would be the most difficult to classify?
•Four organisms that eat similar foods
•Three organisms that are about the same size
•Three organisms that live very close to each other
•Two organisms that look nearly identical

answer; i believe the correct answer is (a)0

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these muscles maintain the blood pressure in the vessels. the smooth muscles are innervated by nerves of the autonomic nervous system. when the muscles contract, they cause vasoconstriction of the vessels and increase blood pressure. when the muscles relax, they enable vasodilation of the   blood vessels hence reduce blood pressure.