Dates are placed on food labels to :

there are several types of dates :

best is used before...= doesn't mean you can't use it afterwards. It's just a way to tell you the best flavor . It is NOT a safety date

Sell by = is NOT a safety date either

Use by = is a safety date unless the products are chilled immediately. This date is the last one recommended  with a high peak of qualityBut you may eat some products afterwards like plain yogurtsanyway, you'll be able to taste if it still good or not.
Avoid fish, meat, not home made food, desert with cream

All those different dates aren't helping  consumers and a lot of food is wasted.

To answer more quickly to your answer it helps microorganisms, as bacteria, yeast,..Among the bacteria , some are pathogenics and may cause foodborne illness

hope I helped 

Ibelieve it's choice d.