How many gills does a shark have on either side of its head?

Explanation

Sharks are different from other fish. Their skeleton is made out of cartilage instead of bone, they have several rows of teeth with enamel in their mouth, 5-7 gills on each side and their abrasive skin was used as sandpaper in the past. The great white shark is the only species that can lift its head out of the water to look for prey. It can grow to be 6 metres long and weigh more than 2 tonnes.