单选题 Different creatures have developed some pretty creative ways to get their rest and stay safe. The lizard likes to sleep at the far end of small branches hanging out over a pond or lake in the rain forest. If a snake tries to slither up the branch to eat it, it will shake the branch and knock the lizard off, and the lizard will fall safely into the water. Chameleons can change color to match their surroundings in order to hide even while sleeping.
Gorillas like to sleep high in the trees. They build a new bed every night, sometimes taking up to hall an hour to pile branches, twigs, and leaves into a comfortable bed. Birds also find it safe to sleep in the trees, but unless they have eggs or young chicks, they don"t use a nest. They just lock their feet around a branch and hang on. A special tendon in their legs is automatically tight when they are at rest, so they won"t let go and fall.
Dolphins live underwater, but must come to the surface to breathe. Scientists now believe that dolphins may sleep with only half their brain, while the other hall stays awake to keep them safe and breathing. Seals also do this, lying on their sides on the surface of the water with one flipper underwater paddling to keep their noses above the surface. Some ducks may also have this ability, and actually sleep with one eye closed and one eye open.

单选题 How many animals are mentioned in this passage?

单选题 How does a chameleon protect itself while sleeping?

单选题 Why will not birds fall when they are at rest?

单选题 Which animals sleep with half brain and half stay awake?

单选题 What does the writer intend to tell us?