What is responsible for holding the lungs to the thorax wall?

Explanation:

Each lung enclosed in two membranes called the pleurae . The outer membrane is called parietal pleura , and the inner membrane is called visceral pleura , which closely invest the lungs . A very narrow space exist between two pleura i.e., known as pleural cavity that contains pleural fluid secreted by the pleurae .  Pleurae cause the production of pleural fluid and create cavities that seperates organ . Mesothelial cells of  both pleural layer secretes fluid and cause lubrication on the surface . These lubrication mimize the friction between  pleural layer to prevent the difficulty in breathing and creates surface tension that  is responsible for holding the lungs to the thorax wall . Generally , pressure within cavities present between pleural layers is less than atmospheric pressure i.e., negative pressure in the pleural cavity which is also  responsible for holding the lungs to the thorax wall .

c) 50% there are four chromosomes. after crossing over, 2 of the four have been changed. that means any gamete has a 2 in 4 chance or 50% chance of receiving the mutated chromosome.