The correct answer is d. peritoneum.
The peritoneum is a continuous membrane that lines the abdominal cavity and covers the abdominal organs. It consists of two layers: the parietal peritoneum, which forms the outer layer lining the abdominal wall, and the visceral peritoneum, which envelops the internal organs. This double-walled structure helps to protect the organs and allows for smooth movement during digestion and other bodily functions.
In contrast, the greater omentum and lesser omentum are folds of the peritoneum that extend from the stomach to other organs, while the mesentery is a fold of tissue that attaches the intestines to the abdominal wall. Therefore, the peritoneum is the correct term for the membrane lining the abdominal cavity.