1) 1. What happens to your heart rate when you exercise? a) It decreases significantly b) It stays the same c) It increases to pump more oxygen-rich blood d) It stops temporarily 2) Which of the following organisms has a closed circulatory system? a) Insects b) Arthropods c) Fish d) Mollusks 3) How do amphibians primarily exchange gases when they are underwater? a) Through their lungs b) Through their gills c) Through their skin d) Through their nostrils

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