Final answer:
Lack of physical activity is most likely to cause constipation as it decreases bowel motility, leading to firmer stools due to increased water reabsorption.
Step-by-step explanation:
The condition most likely to cause constipation among the options provided is c) Lack of physical activity. A high fiber diet and adequate hydration are both beneficial in preventing constipation because they help to maintain a good digestive flow and soft stool consistency. Regular bowel movements are a sign of a healthy digestive system and are unlikely to cause constipation. On the contrary, lack of physical activity can lead to decreased bowel motility, which can cause stool to move through the intestines more slowly, leading to increased water reabsorption and firmer stools, which may result in constipation.