How does Sophie's English nationality and the setting of the novel in England influence the story?
If Sophie was not English, then the setting of the story would be completely different. It's outcome would also potentially be different. For example, if Sophie lived in the United States instead of England, she couldn't just ask the Queen of England for help. She would have to turn to the President of the United States for help instead. The many customs mentioned in the book would also be different. For example, many places around the world do not have tea like the English do.
What are the BFG's motives in taking, then helping Sophie?
The BFG is unlike other giants and believes that giants should not eat humans. He has formed a close friendship with Sophie and wants to help her because he does not want her, or others like her, to get hurt. His affection for humans has only intensified since becoming friends with Sophie.
Compare and contrast the BFG with the rest of the giants.
While the rest of the giants eat humans by the handful, the BFG does not. He prefers to live off of snozzcumbers, even though he doesn't like the taste of that vegetable. The BFG is principled in this way. Once he decided that he wasn't going to eat humans, there was no way he would change. He frowns on the other giants, who do.
The BFG is a gentle soul, collecting dreams and giving them to children. He is also kind to Sophie, as well as caring and loyal, betraying his emotional attachment to Sophie by giving her a kiss on the cheek before leaving her in the palace.
He is also talented, as seen by his super-human hearing.
The other giants are lazy and gluttonous, preferring to just eat humans and nap a little before throwing their youngest giant around. They are bullies and insensitive.
What role does the Queen play in this story?
The Queen facilitates the conclusion of the story. Without her assistance, Sophie and the BFG would have had a much more difficult time trying to stop nine raging giants. The Queen gives Sophie, an orphan, and the BFG, a giant, instant legitimacy in her world. She is respectful and kind to them, and treats them well, even though they are the ultimate outsiders. She verifies their story and then sets about making sure they can accomplish their goal.
Describe how the giants' thirst for humans leads to their downfall.
The other giants are so busy and excited to hunt humans in England that they do not see the BFG and Sophie also running towards England. The giants' single-mindedness has helped the BFG and Sophie on several other occasions. For example, when the Bloodbottler came into the BFG's house thinking he heard the BFG speaking with someone, he is easily distracted by the BFG appealing to his hunger. The BFG offers the Bloodbottler a snozzcumber, which he spits out in disgust and leaves quickly. This gets him out of the BFG's house and helps Sophie escape from his clutches.