Which of the following is a common risk factor for developing pneumonia in animals?

High humidity environments are indeed a common risk factor for developing pneumonia in animals. When humidity levels are elevated, the moisture in the air can create an ideal setting for pathogens, such as bacteria and viruses, to thrive. This increases the likelihood of respiratory infections, including pneumonia, as animals may inhale these pathogens more easily in such conditions. Additionally, high humidity can impact the overall health of the respiratory system, making animals more susceptible to infections.

The other options, while they may have some relevance to animal health, do not have the same established link to pneumonia. For instance, low sugar diets can influence overall health and energy levels but do not directly correlate with respiratory infections. Frequent exercise is generally beneficial for health and immune function, thereby reducing the risk of many diseases, including pneumonia. Lastly, isolation from other animals could decrease exposure to infectious agents; however, prolonged isolation can lead to stress and weaken an animal's immune system, which may also have negative health effects but is not a direct risk factor for pneumonia like high humidity is.