Hippopotamus

Hippopotamus is Greek for "river horse," and the animal has been known since ancient [blank] . Hippopotamuses are often seen basking on the banks or sleeping in the waters of rivers, lakes, and swamps next to grasslands. Hippos are [blank] adapted to aquatic life. The ears, eyes, and nostrils are located high on the head so that the rest of the body may remain submerged. The ears and nostrils can be folded shut to keep [blank] water. The body is so dense that they can walk underwater, where they can hold their breath for five minutes. Although often seen basking in the sun, hippos lose water rapidly through the skin and become dehydrated without periodic [blank] . They must also retreat to the water to keep cool, for they do not sweat.