Dolphins are known as marine (1) ______they breathe air, they are warm-blood, and they bear live young ones called (2) ______.
The size of dolphin is very greatly. (3)______ smallest dolphins are just about 50 kg in weight and 1.2 meters in length (4) ______the largest one can weigh up to 8.200 kg and is 10 meters long.
Dolphins are sociable creatures. They swim together in group known as (5) ______They show great ability in the water. Dolphins are interested (6) ______humans and often rescue people in the sea (7) ______are in danger. They are intelligent creatures and make sounds to (8)_____ with each other. Scientists have studied dolphins (9) _____many years and are now looking into the possibility of dolphins that are able to carry (10) _____ tasks under the sea.