题目内容：

    Dog eyesight declines with age. Injuries and ailments can cloud their vision. Zero was a highly trained, driven alert dog. So, at competitions, when he started running into obstacles and falling off the ends of teeter-totters(跷跷板), his owner, San Francisco-area dog trainer Dianne Morey, was concerned.

As time passed, she noticed a pattern. The problems only occurred at competitions held in horse arenas, where yellow obstacles blended into the color of the sand covering the floor. Concerned about his eyesight, Morey took Zero to a vet, who diagnosed him with a genetic condition. Morey found the diagnosis “heartbreaking”. After one last competition—which he won—Zero retired. In the time since, he’s led a life full of activities like dock diving and hiking, where poor vision is less dangerous. While there’s no cure for his disease, protective eyewear has helped keep him safe while being active.

On average, dogs develop nearsightedness or farsightedness less often than humans, says Alexandra vander Woerdt at Animal Medical Center in New York City. However, their eyesight also declines with age. Injuries and some diseases such as glaucoma(青光眼) can cloud their vision. Thinking back, Morey realizes some behaviors—for instance, the way Zero poked his nose before entering a gate—were signs his vision was impaired.

Identifying vision issues in dogs isn’t as easy as with humans. Dogs don’t bark wrong letters on the eye chart, and they’re very good at adapting. Treatments for eye problems may include eyedrops, medications or surgery. Eyewear can also play a role in treating or preventing many issues. Many dogs don’t like eyewear at first. Zero was an exception, thanks to his training in agility and tricks, Morey says.

1.What made Dianne Morey concerned？

A.Her trained dog Zero fell off in competitions.

B.She was badly hurt by a dog in a competition.

C.She found her eyesight was declining with age.

D.Her trained dog Zero wasn’t as clever as before.

2.What can we know from the second paragraph？

A.Zero is retiring soon.

B.Zero’s disease can’t be cured.

C.Zero got the disease from his birth.

D.Zero has recovered from his poor eyesight.

3.Which of the following can replace the word “blended” in the second paragraph？

A.added.

B.missed.

C.needed.

D.mixed.

4.What makes it difficult to identify dogs’ vision problems？

A.They are too fierce to control.

B.They don’t like to wear eyewear.

C.They adapt to the poor sight easily.

D.They bark wrong letters on the eye chart.