Sentence A is correctly punctuated.
For the other answer choices, a question mark shouldn't be placed.
Cross-Contamination is the procedure by which germs, bacteria or other microorganisms are accidentally transferred or transported from one substance or object to another and one human to another with a very harmful effect. Cross-contamination can be shifted to food by hands, food-contact surfaces and a needle from a syringe that will directly inject into the body.
