C. The author uses a simile to compare the feeling of nervousness to melting because the sentence uses the word "like," which is an underlying hint to similes. Without it, it would be a metaphor.
The first alternative is correct (A).
Stretching is a way to stimulate the muscles and ligaments of the human body to improve posture, breathing and pre-disposition of people. Several activities are part of stretching, such as correct breath control, the time each session should last, and the natural discomfort. However, bounceing the body is not part of stretching practices, it is part of some aerobic activities.
It seems they are asking how the dwarves and goblins being anger at Bilbo, and to compare them with the effects of Bilbo's choice in the book.
