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.
The ways that you can help the students learn more about South Africa include:
Give them an assignment to research on the culture and ethnic groups in South Africa
Students will give a presentation about what they learned about South Africa.
It should be noted that by giving the students assignment on the ethnic groups, they will be able to learn about groups such as Zulu, Xhosa group, etc.
The presentation will also enable other students to learn more about South Africa.