Answer:
Step-by-step explanation:
Salmonellosis is an infection of the intestinal tract caused by consuming water or food contaminated with feces.
Gallstones can cause an obstruction in the bile duct.
Stomach ulcers are usually caused by infection of H. pylori bacteria.
Constipation is not technically an obstruction, but it can lead to obstruction. In this case obstruction seems to be the best choice.
Cholera is a bacterial disease usually spread through contaminated water, so it is an infection.