Final answer:
Elderly individuals are more likely to develop cholecystitis without obstruction, mainly due to age-related factors such as decreased gallbladder motility and changes in bile composition.
Step-by-step explanation:
The individual who is more likely to develop cholecystitis without obstruction is D. Elderly Individuals. Cholecystitis is an inflammation of the gallbladder, often associated with gallstones (cholelithiasis). Gallstones are predominantly made of cholesterol, and their presence in the gallbladder or bile ducts can lead to inflammation, pain, and other complications such as jaundice when a stone blocks the bile duct. While gallstones can occur in any demographic, elderly individuals tend to be at higher risk due to various factors such as decreased gallbladder motility and changes in bile composition with age. In contrast, young adults, individuals with a vegetarian diet, and individuals with gallstones may develop cholecystitis, but it is the elderly who without obstruction are often at higher risk due to age-related changes.