The correct answer is C. lively.
A sprightly young girl is one who is full of life and energy. She is cheerful and animated, and she enjoys being active. She is also often playful and fun-loving.
Sportive means fond of or good at sports. Intelligent means having or showing a high level of mental ability. Beautiful means having a pleasing appearance.
While a sprightly young girl may be any of these things, the word "sprightly" specifically emphasizes her liveliness and energy.
