OPT: 1. air 2. mussels 3. carbon monoxide 4. lava 5. fish 6. open 7. water 8. squids
Q: Fact 1: Gills are used for breathing water by aquatic animals. Fact 2: Shark exhibit Come face to face with the ultimate aquatic predator. Given the two facts above, what are gills used for breathing by sharks?
A:
7.