Answer:
Water.
Step-by-step explanation:
Cystic fibrosis may be defined as the medical condition in which the excess mucus is produced by the body that might affects the lungs and pancreas as well.
This occurs due to the abnormal functioning of chloride channel proteins. The main function of this protein is the transport of the water molecule that helps in the mucus formation. The water moves through the epithelial cells and maintain the role in epithelial fluid and fluid transport.
Thus, the answer is water.