Out of all the available options the correct one would be
He said that he wants to buy this book.
This is because by using the word "said" you are stating something that already happened which was the comment made by the customer. But by using the word "this" you are making connecting the comment to an object which would be the book.
The first interaction between Kumalo and Arthur Jarvis's son leads to B) James Jarvis realizing that Kumalo is the same man whom he met in Johannesburg.
I would start with simple definitions to teach them, the words would depend on the grade they are in, then the words would get harder as we make progress.
Explanation: Hope this helps:).......if not sorry for wasting your time:)