Please choose the correct ending to complete the given sentence: Pets and Animals: [header] How to know if your dog is losing its eyesight [title] Look for cloudy pupils. [step] When a dog's vision begins to suffer with age, you may notice a change to the eye color itself. Cataracts are often a cause of loss of vision related to age, and can be easily seen by looking at your dog's eyes.

Ending1: Your dog may also be looking at its corneas, which are the watery areas inside. [substeps] However, cataracts are usually uncommon in older dogs, especially german shepherds. Ending2: [substeps] Normal eyes may begin to blink brightly for a few seconds and then gradually darken again or lose their whites completely. Cataracts often occur if you pet your dog constantly. Ending3: [substeps] Cataracts are marked by a cloudy appearance around a dog's pupil. Monitor your dog's eyes frequently as it ages, as cataracts are easier to treat and reverse if caught early. Ending4: When a dog develops cataracts, the color becomes darker and take on a bluish complexion. Peripheral peripheral vision in older dogs may also manifest in a bluish complexion.

Answer format: ending1/ending2/ending3/ending4