Please choose the correct ending to complete the given sentence: Pets and Animals: [header] How to diagnose respiratory problems in guinea pigs [title] Listen to your guinea pig breathe. [step] If your guinea pig has a respiratory infection, he may have trouble breathing. Sounds of troubled breathing include wheezing and clicking noises.

Ending1: This might be because his respiratory system isn't working properly and he isn't breathing. [substeps] In the absence of any improvement, your guinea pig may: cough or splutter after sneezing; yelp, as in " yelp, cough, yelp! "; or begin to cough. Ending2: You may hear your guinea pig in a sliding or clipped tone as he breathes. [title] Look for signs of a sinus infection. Ending3: Normal breathing in a guinea pig should be easy and quiet. [substeps] If your guinea pig has allergies, he may breathe more loudly, but probably won't have trouble breathing. Ending4: [substeps] Your guinea pig may cough so you have to take him to the vet. Learn more about respiratory issues by visiting the guinea pig's veterinarian for a blood test.

Answer format: ending1/ending2/ending3/ending4