Final answer:
A decrease in the price of beef (option B) will NOT shift the demand curve for beef; it only changes the quantity demanded along the curve. Options A, C, and D will shift the curve.
Step-by-step explanation:
The factor that will NOT shift the demand curve for beef is B) A decrease in the price of beef. A decrease in the price of a good changes the quantity demanded, not the demand curve itself, because it is a movement along the same demand curve. On the other hand, A) A widely publicized study that indicates beef increases one's bad cholesterol, C) An effective ad campaign by pork producers, and D) A change in the population, will all shift the curve because they change the underlying factors that determine what quantity people are willing to buy at a given price.