IV.阅读理解（共17小题；每小题２分，满分34分）
Like cats, geckos（壁虎）always land on their feet. If they happen to fall from a wall or leaf they’ve been climbing, a quick move of the tail makes sure that they always land on their feet first, a new study finds.
Geckos are truly built for climbing: their feet have hairy toes that can fix themselves to a wall or other vertical（竖直的）surfaces. However, geckos’ feet can’t always keep hold and they may fall to the ground. When geckos fall or jump off a wall, they always land stomach-side down. Geckos’ long tails become necessary during their falls, the new study shows.
Researchers did an experiment. They placed geckos up-side-down on the underside of a leaf. When they lost their foothold and fell, the geckos pitched （倾斜）their tails for balance. They then rotated（旋转）their tails to make their bodies rotate. As soon as they were right-side up, they stopped rotating. On average, it only took the geckos about a tenth of a second to right themselves so that they would land on their feet.
Cats use a different way to land on their feet after a fall. As their tails don’t have the power like geckos’ tails, cats can’t use them to right themselves. Instead they twist their bodies around mid-air.
Engineers are trying to build a robot that imitates the geckos’ climbing ability. A tail will be fixed to the robot to allow it to keep balance.
54. What do we know about geckos?
A. Their toes make it possible for them to walk on walls.
B. Their tails can fix them to a wall or other vertical surfaces.
C. They often land on their backs when they jump off walls.
D. It takes them a second to right themselves in mid-air.
55. How do cats avoid their injury during a fall?
A. By twisting their bodies. B. By fixing their toes to the ground.
C. By using their tails to right themselves. D. By landing upside-down.
56. Geckos’ special abilities have given engineers some new ideas to _________.
A. allow robots to climb vertical surfaces
B. reproduce geckos like robots
C. invent robots that can rotate on the ground
D. invent robots that can balance themselves using their tails
57. What is the text mainly talking about?
A. The interesting living habits of geckos. B. The differences between cats and geckos.
C. Why geckos always land on their feet. D. How geckos climb up vertical walls.
