OA: A web site could be useful for a quick answer but not a very accurate one. Especially since these people arent certified in food.
OB: A book sounds like a very credible place to look for answers but this book is more about personal experiences in diets and isn't certified in food.
OC: An article sounds like a very credible source but is from a person who studied food related problems, meaning that what they have studied isnt as official as an actual certified worker in food.
OD: The most credible source for Ray to choose would be a book on gluten-free diets by an author who has two degrees in nutrition and works at the University of Rockingham.
Zadie Smith had always wanted to dig deeper in her father's war experience, but she never had enough courage to ask him, and neither did he.
One day, Zadie finds herself visiting an American poet friend in Normandy. And when they were visiting the beach there, she realized that it might be the place where, 59 years before, her father landed upon. So, she mentions this to her friend, who was also interested in war history of the area, and as a consequence, Zadie is interrogated by this friend. But in the end, Zadie relaizes she knows nothing about his father's war experence.
After this event, she returns home and feels determined to start interviewing his father.
I have seen both of these used in short stories heck both have been in the same kind of story, as for B and D they both sound like stories that will be more than just a short story.