Read the article and choose the correct answer to each question.
Dolphins are sometimes thought of as the dogs of the sea because they are usually playful and friendly. They're also among the smartest animals on Earth. Dolphins are water mammals. They live in seas and oceans, but they must come up to breathe air. Most dolphins are black or gray.
Dolphins live in groups called schools. They use squeaks and whistles to call each other. Dolphins eat fish and squid. They sometimes die when they are trapped in human's nets.
The smallest dolphin is only 1.2 meters long and weighs 40 kilos. Like a small human child! However, the huge type of dolphin can be 9.5 meters long and weigh around 10 tonnes!
