Read the text below and choose the best answer for each space. Dolphins are amazing animals. Weighing over 1,000 pounds and growing up to 12 feet (1) _ , dolphins are mammals that (2) _ air to survive. Every 15 minutes or (3) _ , dolphins (4) _ to the surface of the water to breathe through a blowhole on top of (5) _ bodies. To continue (6) _ and prevent drowning, (7) _ they rest, dolphins sleep with only half of their brain at a time! They close one eye and (8) _ near the surface, (9) _ the water, swimming slowly and coming (10) _ air. This (11) _ "logging" because the slow-moving dolphins look (12) _ floating logs. There (13) _ about 40 different kinds of dolphins, and they (14) _ use a special ability called echolocation to find (15) _ food in the water. Dolphins send out sound waves that bounce (16) _ objects and come back as echoes that tell (17) _ where the object (18) _ . Dolphins also "talk" to one (19) _ through a series of clicking sounds sometimes making (20) _ 300 sounds per second.