What is the function of serous fluid?

A. It helps the stomach and other organs maintain neutral buoyancy within body cavities, even during fluctuations in atmospheric pressure, or when gases, such as oxygen or methane, are present in varying ratios.
B. It prevents the organs from drying out when in contact with air.
C. It aids in the repair of damaged organs.
D. It enables organs, such as the heart and the stomach, to slide across cavity walls and each other without friction.