Write the next sentence in this paragraph:

How to diagnose respiratory problems in guinea pigs
Listen to your guinea pig breathe.
If your guinea pig has a respiratory infection, he may have trouble breathing. Sounds of troubled breathing include wheezing and clicking noises.

Choose from:
--This might be because his respiratory system isn't working properly and he isn't breathing. 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..
--You may hear your guinea pig in a sliding or clipped tone as he breathes. Look for signs of a sinus infection..
--Normal breathing in a guinea pig should be easy and quiet. If your guinea pig has allergies, he may breathe more loudly, but probably won't have trouble breathing..
--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..
Normal breathing in a guinea pig should be easy and quiet. If your guinea pig has allergies, he may breathe more loudly, but probably won't have trouble breathing.