Choice A reason:

Obesity does not increase the production of bile. However, it can lead to changes in bile composition, increasing the risk of gallstone formation.

Choice B reason:

This statement is incorrect. Obesity is associated with an increased concentration of cholesterol in the bile, which can contribute to gallstone formation.

Choice C reason:

This statement is correct. Obesity increases the concentration of cholesterol in the bile, which promotes gallstone formation. When there is an excess of cholesterol in the bile, it can crystallize and form gallstones.

Choice D reason:

Obesity does not slow down the emptying of the gallbladder. On the contrary, obesity may lead to reduced gallbladder motility, which can contribute to gallstone formation due to stasis of bile.